Whenever I try to restart my Ubuntu either from the command line by typing reboot or in GNOME the computer goes from X to console, starts the shutdown process and then a message saying "[ some number ] Starting new kernel" appears on the screen and the computer goes back to X login screen. I suspect this must have something to do with nvidia drivers, because it seemed to have appeared around the time I bought a new graphic card. Also, when I reboot the second time I see weird graphical artifacts on the screen. When I boot from ubuntu live cd I can reboot just fine. I used jaunty, recently I switched to karmic with no change.

This bug is very annoying, because I have to hard reset my computer in order to reboot. Also not good for the filesystems, I suspect.

Can you suggest a way to debug the cause or if not at least the easiest way to go about reinstalling ubuntu without losing customizations/settings/data?