Sounds like the same trouble that I am having. I've got it down to
where the desktop freezes, except for the mouse pointer. Previously,
even the mouse froze. I have to cold boot at that point. There is also
a huge thread in the Ubuntu forums about freezing problems with over
1,000 posts in it. http://ubuntuforums.org/showthread.php?t=1478787
I've tried 10.04 with freezing problems and 10.10 with freezing
problems. I have a Nvidia card, but as soon as I load nvidia-current I
cannot boot so am using the nouveau driver (no 3D). If you jump to the
middle of the forum thread, you will see that several people have posted
fixes, but no fix seems to work for everyone. This is a new computer
and was working fine until kernel 2.6.32-25 came out for 10.04.