Comment 2 for bug 104745

I have recently run into this same problem as well with a fresh install of Ubuntu 7.10 on a Toshiba R100 as well. After some reading I've found a few other people with the same problem, namely the first link below which is another launchpad bug. As it has been mentioned before, any changes to the display backlight brightness either user initiated with the hot keys or automatically as in letting the computer go idle and dimming the display or switching from AC to battery power causes the strange resolution to be displayed where only the top left quarter of the screen is expanded to full screen on the lcd.

As mentioned above, the proper resolution can be brought back by restarting X or by switching to a virtual terminal with ctrl-alt-F1 and back, ctrl-alt-F7. Some think that ACPI is to blame however when forcing Ubuntu to use the VESA driver, brightness changes work perfectly which makes me think the problem is in the Trident XP4 driver itself.

References of others with similar problems
https://bugs.launchpad.net/ubuntu/+bug/76120
http://ubuntuforums.org/archive/index.php/t-533793.html
http://ubuntuforums.org/showthread.php?p=4305081#post4305081

Any help on this issue would be greatly appreciated.