I just upgraded from Ubuntu 11.10 to 12.04 and when I tried to install Dropbox it froze at 99%. Then I hit the reset button and I lost the control panel on top and the launcher. I then tried Ctrl+Alt+F1 and nothing happened. Any advice?
This is two separate issues.
To force recovery of your GUI, then remove and re-install from text-console mode. This should fully recover, but will not affect any files, folders you have (presumably also backed-up).
Once you re-start your machine, and resolve any issues with 'control panel' and 'launcher' then follow instructions at: