Terrible mouse problem

My mouse has become unusable. It's been this way for five days now...on boot up to the desktop, the mouse cursor starts out down and to the right of the upper left corner of the screen (about six inches "southeast" on my 30-inch screen) and it's unusable because whenever I move the mouse, the cursor continuously snaps back to its original position. If I safe boot all is fine and I know it's not a hardware issue. Something I've installed or updated is causing this and it's driving me nuts... I've removed preference panes, and start-up items but can't seem to find the conflict. I do not remember doing anything to bring this on but you can't use a mouse-driven GUI if you can use the mouse...

I had been using the bluetooth magic mouse and had downloaded a pref pane for it, but I've deleted the pref pane, removed the magic mouse and am now using a wired mighty mouse but the problem persists.

Looking for help.