Mouse Speed Changes Randomly / Jumps Around Screen...

Hello,

Only for the past couple of months (after about 4 years with no problems) my mouse has had a mind of its own. It stops working, then starts working. Slows down, acts normal, then stops. Sometimes it works ok and sometimes it works terribly. I assume it's software related but I can't find the software to check. Basically, everything on my iMac is still "stock" except for the 512mb of memory I put in today. The mouse (optical Pro Mouse) and keyboard are the original. The keyboard still works fine.

I've done the following to try and fix the problem:

*plugged mouse directly into computer usb unplugged all other items (just printer and keyboard)

*ran hardware test disc (everything was fine)

*recently added memory

*rebooted computer several times

*switched back and forth from OS9 to OSX (didn't have any problems in OS9)

*tried different usb ports on keyboard



I'm not sure what else to try outside of upgrading OS and getting a new keyboard and mouse, rebuilding the desktop (whatever that does), or reinstalling the OSX.

Any other suggestions?

Thanks,

Todd