Ubuntu :: 11.04 - Mouse Randomly Stops Working Inside Applications?

This happens randomly after a reboot: I can move the mouse cursor and it works perfectly only on the Unity sidebar or whatever it's called. I can fire up applications, but once they're up they completely ignore any clicks or mouse movements (the main menu does not appear on the top bar if I move the cursor in the location that usually makes it appear). They only recognise a click on the close/iconize/maximize buttons.

The mouse works: as I said I can move the cursor and it recognises clicks on the sidebar and the window control buttons; plus, it's connected via a KVM switch both to the Linux box and to a Windows box (from which I'm writing this) and in Windows perfectly.The pattern used to be this: usually while running Firefox, the mouse and keyboard stop responding, and sometimes the whole desktop graphics become corrupted. I can Alt+F1 and go to a text-mode console, but nothing short of a reboot "fixes" things. After the reboot, about two times out of five everything works, three times out of five I get the situation described above.

For the last few hours or so, however, no amount of rebooting and sacrificing goats to the gods protecting sociopaths and Linux software developers have been able to restore mouse functionality. I click on my username on the login windowhere it works perfectly), enter the password and then only the Unity sidebar works: again, the mouse cursor moves, only clicks (right and left) are ignored, as are hotspots. In ubuntu classic there is no place where I can click and launch applications, btw - once I get in I'm basically blocked and can't do anything