Ubuntu 11.10 works really well with my Nvidia GTS 450 except that when I try to change to a tty (Ctrl+Alt+F1 to F6) all I get is a black screen. I can get back to Gnome Shell with Ctrl+Alt+F7.
I believe I'm using the 280.13 driver.
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I would try disabling the proprietary driver first, and see if that works. If it doesn't, then try accessing the terminal from a different session (Ubuntu, Ubuntu 2D, ect). If it works from there, I would try disabling any Gnome Shell extensions you have enabled, or simply reinstalling Gnome Shell.
Plymouth (splash), while nice, is known to cause some issues. Sometimes disabling it will bring back the console.
To try it, reboot, and choose recovery console in GRUB. Then, in recovery mode, choose boot normally and see if your