When I connected my serial to USB converter (USB-Comi) to my computer my mouse pointer would randomly jump around the screen making it impossible to do any work. I tried reinstalling both the serial to USB converters drivers and my mouse drivers without an success.
After some searching I found this article How to fix “crazy mouse” syndrome with USB serial adapters that was able to resolve the issue I was having.
You need to disable serial enumeration on the advanced settings of your virtual serial port. The serial port will still work and it should resolve your “crazy mouse” problem.