Originally posted by SlackerLX
CTRL+ALT+F7 - Desktop Env
The CTRL actually isn't needed. It's simply ALT+F7.
As for your problem, try restarting X. You can usually do this with CTRL+ALT+Backspace. If this doesn't work, you can always open one of the pseudo-terms (CTRL+ALT+F1 through F6) and restart it manually.