o.k, this is embarrassing:
I have installed Compiz Config Settings Manager and tried to fix it so that the transition time between changing tabs (using alt+tab) will be short. by accident I un-pressed V from something else, and it asked me about a conflict - I pressed the "x" button to close the window and as a result I stopped seeing the unity interface. That is - I can not see any buttons of the left side.
I went to the terminal (ctrl+alt+F1) and ran
As a result I got the following error:
$ ccsm /usr/lib/python2.7/site-packages/gtk-2.0/gtk/__init__.py:57: GtkWarning: could not open display warnings.warn(str(e), _gtk.Warning) Traceback (most recent call last): File "/usr/bin/ccsm", line 93, in <module> import ccm File "/usr/lib/python2.7/site-packages/ccm/__init__.py", line 1, in <module> from ccm.Conflicts import * File "/usr/lib/python2.7/site-packages/ccm/Conflicts.py", line 26, in <module> from ccm.Constants import * File "/usr/lib/python2.7/site-packages/ccm/Constants.py", line 29, in <module> CurrentScreenNum = gtk.gdk.display_get_default().get_default_screen().get_number() AttributeError: 'NoneType' object has no attribute 'get_default_screen'
What should I do next?