"This issue isn't limited to feisty, it affects edgy too!

I have been fighting this lock-up issue for some time & have not pinned it
down yet, seems wide spread & wide assortment of hardware. I think it's the
generic kernel.

I'm backing stuff up & will try some of the so called obsolete kernels, what
can it hurt? This box is pretty limited w/o nvidia drivers. If load I them
from the repositories or using envy this box locks up all the time. Firefox
open & screensaver tries to load, just push the reset as it's toast."

#160 at http://ubuntuforums.org/showthread.php?t=412125&page=16

Linux just works.