My system has been stable for about 3 months then without warning I started to get a freeze of the display and then a problem report saying GPU hung.
I have update the graphics driver as per How to install Intel 82852/855GM driver? so I know that I have the latest driver available but I still keep getting, and reporting, regular GPU hang messages. Now every now and then the screen freezes in a big way and I can only proceed by ssh in from a separate machine and killing off lightdm and then restarting it and logging in again.
If anyone has fixed this problem it would be good to know the solution.