Hello,
I have just received a new Dell computer shipped with Ubuntu 11.10.
Upon reception, everything worked fine. Today I decided to make the software updates suggested by Ubuntu.
After reboot I found a graphical glitch on the top of my screen: it is a ~10px band that constantly blinks. More rebooting didn't help. Logging on another user account didn't help.

My investigation so far :
* my GPU is a Intel SandyBridge Mobile
* my glxinfo output is
Code:
$ glxinfo
name of display: :0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.4
server glx extensions:
    GLX_ARB_multisample, GLX_EXT_import_context, GLX_EXT_texture_from_pixmap, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer, 
    GLX_OML_swap_method, GLX_SGI_make_current_read, GLX_SGI_swap_control, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_INTEL_swap_event
client glx vendor string: Mesa Project and SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_EXT_framebuffer_sRGB, 
    GLX_MESA_copy_sub_buffer, GLX_MESA_multithread_makecurrent, 
    GLX_MESA_swap_control, GLX_OML_swap_method, GLX_OML_sync_control, 
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_EXT_texture_from_pixmap, 
    GLX_INTEL_swap_event
GLX version: 1.4
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer, 
    GLX_MESA_multithread_makecurrent, GLX_MESA_swap_control, 
    GLX_OML_swap_method, GLX_OML_sync_control, GLX_SGI_make_current_read, 
    GLX_SGI_swap_control, GLX_SGI_video_sync, GLX_SGIS_multisample, 
    GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, GLX_SGIX_visual_select_group, 
    GLX_EXT_texture_from_pixmap, GLX_INTEL_swap_event
OpenGL vendor string: Tungsten Graphics, Inc
OpenGL renderer string: Mesa DRI Intel(R) Ivybridge Mobile 
OpenGL version string: 2.1 Mesa 7.11
OpenGL shading language version string: 1.20
OpenGL extensions:
    GL_ARB_multisample, GL_EXT_abgr, GL_EXT_bgra, GL_EXT_blend_color, 
    GL_EXT_blend_logic_op, GL_EXT_blend_minmax, GL_EXT_blend_subtract, 
    GL_EXT_copy_texture, GL_EXT_polygon_offset, GL_EXT_subtexture, 
    GL_EXT_texture_object, GL_EXT_vertex_array, GL_EXT_compiled_vertex_array, 
    GL_EXT_texture, GL_EXT_texture3D, GL_IBM_rasterpos_clip, 
    GL_ARB_point_parameters, GL_EXT_draw_range_elements, GL_EXT_packed_pixels, 
    GL_EXT_point_parameters, GL_EXT_rescale_normal, 
    GL_EXT_separate_specular_color, GL_EXT_texture_edge_clamp, 
    GL_SGIS_generate_mipmap, GL_SGIS_texture_border_clamp, 
    GL_SGIS_texture_edge_clamp, GL_SGIS_texture_lod, GL_ARB_framebuffer_sRGB, 
    GL_ARB_multitexture, GL_EXT_framebuffer_sRGB, 
    GL_IBM_multimode_draw_arrays, GL_IBM_texture_mirrored_repeat, 
    GL_3DFX_texture_compression_FXT1, GL_ARB_texture_cube_map, 
    GL_ARB_texture_env_add, GL_ARB_transpose_matrix, 
    GL_EXT_blend_func_separate, GL_EXT_fog_coord, GL_EXT_multi_draw_arrays, 
    GL_EXT_secondary_color, GL_EXT_texture_env_add, 
    GL_EXT_texture_filter_anisotropic, GL_EXT_texture_lod_bias, 
    GL_INGR_blend_func_separate, GL_NV_blend_square, GL_NV_light_max_exponent, 
    GL_NV_texgen_reflection, GL_NV_texture_env_combine4, 
    GL_SUN_multi_draw_arrays, GL_ARB_texture_border_clamp, 
    GL_ARB_texture_compression, GL_EXT_framebuffer_object, 
    GL_EXT_texture_env_dot3, GL_MESA_window_pos, GL_NV_packed_depth_stencil, 
    GL_NV_texture_rectangle, GL_NV_vertex_program, GL_ARB_depth_texture, 
    GL_ARB_occlusion_query, GL_ARB_shadow, GL_ARB_texture_env_combine, 
    GL_ARB_texture_env_crossbar, GL_ARB_texture_env_dot3, 
    GL_ARB_texture_mirrored_repeat, GL_ARB_window_pos, GL_ATI_envmap_bumpmap, 
    GL_EXT_stencil_two_side, GL_EXT_texture_cube_map, GL_NV_depth_clamp, 
    GL_NV_vertex_program1_1, GL_APPLE_client_storage, GL_APPLE_packed_pixels, 
    GL_APPLE_vertex_array_object, GL_ARB_draw_buffers, 
    GL_ARB_fragment_program, GL_ARB_fragment_shader, GL_ARB_shader_objects, 
    GL_ARB_vertex_program, GL_ARB_vertex_shader, GL_ATI_draw_buffers, 
    GL_ATI_texture_env_combine3, GL_EXT_shadow_funcs, GL_EXT_stencil_wrap, 
    GL_MESA_pack_invert, GL_MESA_ycbcr_texture, GL_ARB_depth_clamp, 
    GL_ARB_fragment_program_shadow, GL_ARB_half_float_pixel, 
    GL_ARB_point_sprite, GL_ARB_shading_language_100, GL_ARB_sync, 
    GL_ARB_texture_non_power_of_two, GL_ARB_vertex_buffer_object, 
    GL_ATI_blend_equation_separate, GL_EXT_blend_equation_separate, 
    GL_OES_read_format, GL_ARB_color_buffer_float, GL_ARB_pixel_buffer_object, 
    GL_ARB_texture_compression_rgtc, GL_ARB_texture_rectangle, 
    GL_EXT_pixel_buffer_object, GL_EXT_texture_compression_rgtc, 
    GL_EXT_texture_rectangle, GL_EXT_texture_sRGB, GL_ARB_framebuffer_object, 
    GL_EXT_framebuffer_blit, GL_EXT_framebuffer_multisample, 
    GL_EXT_packed_depth_stencil, GL_APPLE_object_purgeable, 
    GL_ARB_vertex_array_object, GL_ATI_separate_stencil, GL_EXT_draw_buffers2, 
    GL_EXT_gpu_program_parameters, GL_EXT_texture_env_combine, 
    GL_EXT_texture_sRGB_decode, GL_EXT_timer_query, GL_OES_EGL_image, 
    GL_ARB_copy_buffer, GL_ARB_half_float_vertex, GL_ARB_map_buffer_range, 
    GL_ARB_texture_rg, GL_ARB_texture_swizzle, GL_ARB_vertex_array_bgra, 
    GL_EXT_separate_shader_objects, GL_EXT_texture_swizzle, 
    GL_EXT_vertex_array_bgra, GL_NV_conditional_render, 
    GL_ARB_ES2_compatibility, GL_ARB_draw_elements_base_vertex, 
    GL_ARB_explicit_attrib_location, GL_ARB_fragment_coord_conventions, 
    GL_ARB_provoking_vertex, GL_ARB_sampler_objects, GL_ARB_seamless_cube_map, 
    GL_ARB_shader_texture_lod, GL_EXT_provoking_vertex, GL_EXT_texture_snorm, 
    GL_MESA_texture_signed_rgba, GL_ARB_robustness

32 GLX Visuals
    visual  x   bf lv rg d st  colorbuffer  sr ax dp st accumbuffer  ms  cav
  id dep cl sp  sz l  ci b ro  r  g  b  a F gb bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------------
0x021 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x022 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0a0 24 tc  0  24  0 r  . .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0a1 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0a2 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0a3 24 tc  0  24  0 r  . .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0a4 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0a5 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0a6 24 tc  0  32  0 r  . .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0a7 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0a8 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0a9 24 tc  0  32  0 r  . .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0aa 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0ab 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8 16 16 16  0  0 0 Slow
0x0ac 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0ad 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8 16 16 16 16  0 0 Slow
0x0ae 24 dc  0  24  0 r  . .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0af 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0b0 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x0b1 24 dc  0  24  0 r  . .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0b2 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0b3 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0b4 24 dc  0  32  0 r  . .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0b5 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0b6 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x0b7 24 dc  0  32  0 r  . .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0b8 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0b9 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x0ba 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8 16 16 16  0  0 0 Slow
0x0bb 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x0bc 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8 16 16 16 16  0 0 Slow
0x06f 32 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None

48 GLXFBConfigs:
    visual  x   bf lv rg d st  colorbuffer  sr ax dp st accumbuffer  ms  cav
  id dep cl sp  sz l  ci b ro  r  g  b  a F gb bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------------
0x070  0 tc  0  16  0 r  . .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x071  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x072  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x073  0 tc  0  16  0 r  . .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x074  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x075  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x076 24 tc  0  24  0 r  . .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x077 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x078 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x079 24 tc  0  24  0 r  . .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x07a 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x07b 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x07c 24 tc  0  32  0 r  . .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x07d 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x07e 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x07f 24 tc  0  32  0 r  . .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x080 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x081 32 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x082  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x083  0 tc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0 16 16 16  0  0 0 Slow
0x084 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x085 24 tc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8 16 16 16  0  0 0 Slow
0x086 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x087 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8 16 16 16 16  0 0 Slow
0x088  0 dc  0  16  0 r  . .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x089  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x08a  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0  0  0  0  0  0  0  0 0 None
0x08b  0 dc  0  16  0 r  . .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x08c  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x08d  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x08e 24 dc  0  24  0 r  . .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x08f 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x090 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0  0  0  0  0  0  0  0 0 None
0x091 24 dc  0  24  0 r  . .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x092 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x093 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x094 24 dc  0  32  0 r  . .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x095 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x096 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0  0  0  0  0  0  0  0 0 None
0x097 24 dc  0  32  0 r  . .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x098 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x099 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x09a  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0  0  0  0  0  0 0 None
0x09b  0 dc  0  16  0 r  y .   5  6  5  0 .  .  0 16  0 16 16 16  0  0 0 Slow
0x09c 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8  0  0  0  0  0 0 None
0x09d 24 dc  0  24  0 r  y .   8  8  8  0 .  .  0 24  8 16 16 16  0  0 0 Slow
0x09e 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  0 0 None
0x09f 24 dc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8 16 16 16 16  0 0 Slow
* I tried reverting xserver-xorg-video-intel to the previous version using synaptic but it did not change a thing
* if I use a second monitor there is no glitch on the second monitor
* if I use a second monitor and disable my laptop's screen then the glitch moves to the second monitor

Any idea what to do to fix this ?
Thanks in advance.