
Firefox 16, Ubuntu 12.04, Gnome Classic Session, Compiz effects enabled. Is this a bug? Anybody else having this? What shall I do?
Open a terminal and install compizconfig-settings-manager
sudo apt-get install compizconfig-settings-manager
Then open it by going to Menu → System tools → Preferences in Gnome-classic.
Click on the Preference button on the left side (bottom)
In the Profile section, there is a button named Reset to defaults. Click on that button. Wait.... and then Logout from the session
Login again to see the result
Note: If the resetting get frozen, Try to Logout from the session forcefully, by using Ctrl-Alt-Del keyboard shortcut.