I recently upgraded my Ubuntu installation from 9.10 (with the old 8.10 video drivers that didn’t crash) to 10.04. I immediately began seeing the video crash, especially when there was a lot of activity.
It turns out I have an Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device (rev 01). This is one of the many Intel video cards that have trouble.
I applied workaround F from here: https://wiki.ubuntu.com/X/Bugs/Lucidi8xxFreezes
That led me to here: http://www.ubuntugeek.com/intel-graphics-performance-guide-for-ubuntu-904-jaunty-users.html
After applying the Method 2 fix from there, things seem to be a little more stable. Time will tell.