Hey flower, one thing I noticed a long time ago with Ubuntu 11.04 at least is that at times, with numerous cards, depending on board, you just see a black screen and the monitor will goto power save mode. Push ALT-F1, SHIFT-ALT-F1, CTRL-ALT-F1. Usually alt-f1 will work, but it is just wonkiness with the graphics display xvga settings in Grub.
You should get a screen. You can test if the box is truly locked up by once the black screen happens, push your caps lock key, if light no keyboard lights up, you're not locked up* so to speak.
Try the method I mention above and just push ALT-F1 or other combination(s) a few times and see what happens
