I reboot my desktop the other day, entered my username/password @ the gdm login, heard the pretty Ubuntu music and saw Gnome loading, when all of a sudden, *poof*, I was back at the gdm login screen being prompted for my username. Hmm I thought.


In /var/log/Xorg.0.log, the following existed:
AUDIT: Sat Jan 20 19:50:40 2007: 5351 X: client 2 rejected from local host


After Googling around a bit,the solution was to re-install my NVIDIA driver as the libglx.so symlink was broken (at /usr/lib/xorg/modules/extensions/libglx.so). Downloading and installing NVIDIA-Linux-x86-1.0-9631-pkg1.run corrected the issue. libglx.so is symlinked to libglx.so.1.0.9631 in the same directory.