Question : iMac Snow Leopard Mouse pointer jitter and always go back to upper left corner

I am using the latest iMac 27" with Snow Leopard. The magic mouse suddenly not correctly response to the movement. When I move the mouse, the pointer always jumps back to the upper left corner. I plugged in a regular usb mouse, it is the same thing. It seems something wrong in the OS. Any help?

Answer : iMac Snow Leopard Mouse pointer jitter and always go back to upper left corner

Is the second mouse optical, also?  If so, you need to use the mouse on a flat surface that has a texture or a pattern that changes so the optics can determine where the mouse has moved.  Try a mouse pad or even a cutting board.