Ubuntu :: Holding Down Left Mouse Button Has No Effect?

About a week ago I did a fresh install of Maverick on somebody else's laptop. Everything was fine at first, but a couple of days ago the person contacted me saying that they weren't able to move or resize windows anymore. (The only thing that does work with respect to moving a window is initializing the action by pressing Alt+F7.) Later we found out that they also can't drag and drop files or use the mouse to drag scrollbars up and down. So basically, they can't do anything that is usually done by holding down the left mouse button and moving the pointer. I've already tried the following things to make it work again:

- playing around with the mouse settings

- checking in CCSM whether the 'move window' and 'resize window' plugins were enabled

- setting desktop effects to NONE in the visual effects tab in 'appearance'

- using compiz fusion icon to (1) reload window manager and (2) switch from compiz to metacity for window management

- deleting folders containing GNOME settings from home folder (.gconf, .gconfd, .gnome2, .gnome2_private), logging out and back in afterwards to automatically create new configuration files

I've been doing a lot of googling about this but I'm running out of ideas. Most people (there don't seem to be that many) that have had a similar problem are saying that it's got something to do with compiz, and disabling it solved the problem for most of them. But in my case - no dice.