Cursor jumps erratically

I have a very high end user who says his cursor jumps erratically quite often. He is a CAD person so it annoys him quite a bit. I have switched out his mouse and he still has the problem. He is running Windows 2000 on a Dell Precision Workstation330 with a Fire GL2 card. I have updated the video drivers and this erratic movement still occurs. Any ideas? He also says that documents will actually move (drop and inch or 2). Thanks.