Comment 1 for bug 114065

Eric Feliksik (milouny) wrote :

I confirm this problem on my 2GHz white MacBook with Ubuntu Feisty.
Sometimes Ubuntu boots with this problem, sometimes it happens out of the blue while working. Plugging in a usb-mouse, or removing it, sometimes creates or solves the problem.
OS X doesn't have this problem.

There are more people reporting this bug: http://ubuntuforums.org/showthread.php?t=439541 (page does not give a solution other than plugging/unplugging usb mouse)