This happens many times here - trying Linux options & apps. I simply re-install Ubuntu. It 'remembers' my previous settings. Since my notebook hardware cannot handle COMPIZ, it will not allow me to install it at all. No Compix 11.04 on my simple Intel I3 cpu. :-(
When reinstalling, use the manual partition setup. Select exactly the same ROOT, BOOT & SWAP partitions are the previous setup. ROOT is about 16 gigabytes, since it has most of the folders of Linux. BOOT is 512 megabytes. SWAP is 4 GB, enough for hibernation if needed.