Same problem but I have a logitech cordless mouse. If I unplug the receiver dongle, the mouse continues to creep. Mine seems to be random but it's annoying. It seems to do it most during startup and when the PC has been idle for a little while and when I load a web page.

I have tried all sorts of malware/spyware and AV scans and come up with nothing every time. I have also tried uninstalling and re-installing the drivers. The only thing left now is to do a windows re-install from what I can see.