Yesterday I upgraded from 12.10 to 14.04 by
Things were Ok after the upgrading.
However today when I logged into my account, no menu bar, no unity launch.
I tried ctrl+alt+F1 to open the terminal and re-installed Ubuntu-desktop, but it didn't help.
Then I installed compizconfig-settings-manager. But
ccsm failed with the error message
could not open display.
The only good news was that when I logged in as guest, the desktop worked fine.
What can I do now?
First thank you all.
According to Upgrade from 13.10 to 14.04 no unity dash for default user special compiz config, I deleted
~/.cache/compizconfig-1 and the problem was solved.
I think this was caused by my own configuration files. And definitely bain's method will work too.
I opened TTY because I failed to run terminal by ctrl+alt+T. I didn't realize
ccsm couldn't work in that situation.
Thank you once again.