Thomas et alia,
I've notice lately some odd effects with the graphics on my pangolin (panp4n). I am currently running System 76 driver 2.3.0 on Ubuntu 8.10. I never noticed the problems before the driver was updated from 2.4.x.
Generally, it shows as "artifacts" when graphics are scrolled (like when you are scrolling up and down in OpenOffice -- there is leftover text on the screen so that you see it in both the new and old position).
I'm only latched on to the System 76 driver because I started seeing this when the driver updates hit. It could well be something else, but I have to start somewhere.
Checked the NVidia drivers, seemed fine (and the same as they were before the problem showed up).