Mouse moving to the same location

[Tim]

Something strange started happening last night with my wife's computer. 
Her mouse keeps moving to the same location once you let go of 
it(towards the middle of her monitor) only thing I could find that 
mentioned this on any forums or blog was to someone who had a similar 
issue (cursor kept moving to lower corner of the monitor) and they 
reinstalled compiz to fix it. That didnt work for her. I also changed 
the physical mouse and usb port it was connected to just in case it was 
a hardware issue. To sort of triple check a hardware issue I also 
connected through VNC and the same issue occurred so I removed the mouse 
and rebooted the system. Tried through VNC and it still moves to the 
same spot on the screen.

Any ideas on this would be great. It has me stumped.

Thanks!