[SOLVED] Black screen after user switch

[VictorR]

Since recently switching users became a problem. There are two users, myself and my wife. When she switches to her account, everything goes Ok, but when clicks Log Out or chooses my account in the Switch User applet, after login I get black screen and the cursor moving. Have not found any way to get out of this state, except pressing Reboot button on the box.
The system is: Ubuntu 8.10 Intrepid,
kernel: 2.6.27-7-generic
Video: NVidia GeForce 4 Mx440 64 MB
driver: nvidia-glx-96 96.43.09-0ubuntu1 from Proposed repositories
Monitor: Philips 220WS (widescreen), resolution 1680 * 1050
XOrg.conf:

# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig: version 1.0 (buildmeister@builder57) Mon Oct 27 14:37:20 PST 2008

Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "Module"
Load "dbe"
Load "extmod"
Load "type1"
Load "freetype"
Load "glx"
EndSection

Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
EndSection

Section "Monitor"
Identifier "Monitor0"
VendorName "Unknown"
ModelName "Unknown"
HorizSync 30.0 - 110.0
VertRefresh 50.0 - 150.0
Option "DPMS"
EndSection

Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
Option "AddARGBGLXVisuals" "True"
SubSection "Display"
Depth 24
Modes "1680x1050" "1600x1200" "1280x1024" "1024x768" "800x600" "640x480"
EndSubSection
EndSection

Never experienced this before with Hardy.
Thanks in advance for any help.

[VictorR]

According to this bug report (https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/112518) the cure might be un-ticking "Sync to VBlank". In my case I did it for both:
1. System -> Preferences -> CompizConfig Setting Manager -> General -> General Options -> Display Settings tab -> Sync to VBlank (cleared)
2. System -> Administration -> NVidia X Server Settings -> X Server 0 ->
2.1 X Server XVideo Settings
2.2 OpenGL Settings
All "Sync to VBlank" checkboxes are cleared.