Try removing "splash" or adding "vga=0x31a" in /boot/grub/menu.lst in the line starting with "# defoptions=quiet splash", then do sudo update- grub and restart.
Taken from http://wiki.ubuntuusers.de/Nvidia_Grafikkarten -- edgy: usplash (?) blocks console after kdm shutdown https://launchpad.net/bugs/67440 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
