Ive got a cheap compusa brand (MS takeoff) optical mouse. The problem is this; I let go of the mouse and periodically the cursor moves by itself towards the top of the screen or left of the screen even though no physical movement is occuring. I tried another mouse (one with a ball) and it worked w/o problems. Both mice connect via USB. This only started happening after XP SP2. Was wondering if anyone else had this happen, or is it a bad mouse...