Are you using an NVIDIA graphics card? The 'nouveau' driver is the experimental open-source 3D acceleration driver for NVIDIA cards. You may want to try using something like the 'nv' driver or the generic 'vesa' driver to get more stability. You won't have 3D acceleration, but it should at least let you get to a working desktop. Also, if you're on Ubuntu (as your profile says), it should provide the NVIDIA binary-only drivers (should work perfectly, with 3D acceleration) as a package in the software repositories. You can just go into Synaptic and look for 'nvidia', and you should be able to find the appropriate package.
Last edited by MrCode; 07-11-2010 at 03:36 PM.