This problem has me stymied

[reprobate]

I've been using a MS trackball explorer with my iMac G5 since I bought it in January. Suddenly the two right buttons which I programmed for forward and back have stopped working. I tried uninstalling the Intellipoint software and reinstalling. I also have a MS trackball optical for my iBook and tried that on the iMac and the trackball explorer on the iBook. Both work on the iBook but both show the same problem on the iMac, which says to me that it's a software problem on the iMac.

I even restored from my firewire external backup drive and the iMac worked for a minute but then the same problem showed up. I can't figure out why something that has worked fine for months suddenly shows such strange behavior.

Anyone ever have something like this happen, or shall I call an excorcist?