sMoKiE,
Looks like my mouse is having a problem also. Was working fine with the PS/2 - USB adapter. After I plugged in my serial cable for my UPS, the mouse has completely disappeared from the system. Going to find out where it went ...
Note: Just rebooted, and it's back. This is a dumb question because I can't find if you answered it already, but how's your mouse connected?
I keep noticing with mine, if I move around the adapter, it works.