I have Ubuntu 12.10 installed on my machine (not in VirtualBox). It has been there for about two years (I upgraded from 11.04). I am using the default Unity user interface.
Today copy/paste just stopped working! In NetBeans, Gedit, Firefox, etc. it also doesn't work neither with the keyboard nor with the mouse. When I copy some text (Ctrl+C or right-click -> Copy), I still have the Paste mouse menu item disabled.
However, in the terminal Ctrl+Insert and Shift+Insert work well, while Shift+Ctrl+C and Shift+Ctrl+V don't work.