Just started using ubuntu on a machine and I'm also using a new video card. The system has freezed up a couple of times in the last hour. The display remains static, and the mouse cursor does will not move. Any ideas what could cause this?
My guess is a driver problem between the OS and your new video card.
Revert to the old card and look up new drivers, and search around to see if anyone else has had this issue with Ubuntu and this particular card. The Ubuntu Forums, particularly the Installation & Upgrades board would probably be of good use.