Laptop Screen issue - Acer Aspire 1360

Hi folks,
I've been struggling to get the correct resolution working on an Acer Aspire 1360 model for some 6 months. Ubuntu 11.10 works fine, except for this VGA issue. Can anyone shed any light on this problem as I'm really keen to steer away from winXP or a Linux Mandriva strain and REALLY want to stay with Ubuntu.
I've attached a photo of the laptop's screen problem so people can see actually what has happened, namely the VGA output is only some 70% of the screen (as you can see, there is a 2ins/5cm blank column on the right of the screen output). It's not a hardware problem as the original MS XP Home which came with the unit as new, works fine without any similar problems so I presume it's the Openchrome (SIS). The computer 'share's the memory for VGA, I've tried reducing the BIOS 64meg shared VGA to 32meg (makes no difference) and the laptop has a total of 736Meg (512+256=768-32meg) RAM, but I doubt that the RAM size is the problem.


xrandr:
Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 800 x 600, maximum 800 x 600
default connected 800x600+0+0 0mm x 0mm
800x600 60.0* 56.0
720x576 60.0
800x480 60.0
720x480 60.0
640x480 60.0



Any advice/comments on this issue is most welcome.
Thanks in advance.

Paul B,
Lancs, UK.