Compiz has a hotkey combo to slow down animations (very drastically). Chances are that you've accidentally pressed this hotkey combo and now all the animations are very slow.
To see what the hotkey combo is, run 'ccsm' (compiz settings), click on the 'general' icon, and go to keybindings. If this key combo is set, then try pressing it and see if that fixes the problem. If the 'slow anims' keybind is not set, then set a keybinding for it, log out and log back in, then try it out and see if that fixes the problem.