How to Temporarily Disable Pen Input on Ubuntu (Jaunty) on Thinkpad X41

How to Temporarily Disable Pen Input on Ubuntu (Jaunty) on Thinkpad X41

I have a Thinkpad X41 tablet PC on which I installed Ubuntu. Everything works fine, including pen input. However, there is a hardware problem which causes the mouse to erratically jump to the bottom of the screen (the problem occurs under both Windows and Linux). It seems to be linked to humidity or static or something. Since it occurs erratically, I need to disable pen input temporarily.