The long arm of coincidence

The trackball kept locking up and behaving erratically, with the pointer staying stuck at one edge of the screen, then moving when my hands were completely away from ball and keyboard—and Logitech support could only say, “Well gee, the new Mouseware drivers were supposed to fix it,” so I finally ran over to Office Depot and bought a very cheap mouse, to see whether I had a hardware failure coincidental to the Windows service pack installation.  I plugged in the mouse, cranked up the box—and everything worked properly.  It’s this kind of thing that runs techies insane.