Touchpad & TrackPoint (ThinkPad L520) suddenly unresponsive

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http://askubuntu.com – My mother has a problem with her ThinkPad L520 notebook (Ubuntu 11.10, Unity). She boots the device, everything works fine at first. But then, out of nowhere, her touchpad + trackpoint stop working. She can't click or drag the mouse. If she connects an external mouse, she can move the pointer and click (but the internal touchpad or trackpoint still don't work). She already updated everything through the update manager, but still no success...like I said, sometimes it works, sometimes it doesn't. There are no 'special' mouse drivers installed. What can I do to fix this? Thank you for your help (HowTos)