It sounds like either the mouse.sys or a software problem with an addon. If
you are running a program like Logitech or Microsoft optical try a removal and
reinstall to correct this. If not the question here is which version of Windows
you are running. With XP you could try the system file checker with the entry
of "sfc /scannow" if you have an installation disk onhand or a restore point.
(Note: sfc /scannow is typed in at the Run prompt on the Start menu or in
the Command prompt in Accessories.)
