Comment 26 for bug 969039

I have a theory...

It's possible the problem here is nautilus binding Alt+Left/Right combos on the desktop window, as it does with regular nautilus windows. If that's true, then any Alt+Left/Right eveht not completely bound to the active application will be absorbed by the nautilus desktop window. And so compiz can't receive the event (at the root window) to know that Alt was used with some other key and it thinks just Alt was tapped.