Sometimes we end users figure things out for ourselves (thank God I didn't call the IT guy!!)
Came into work, started computer. Went to open an application...the mouse wouldn't work. Not a prob--used the arrow keys & opened application (from desktop). Anyway, couldn't navigate (mouse STILL not working). One of my co-workers was standing there & I told her I needed a new mouse-mine had died. Moved it around some more, still not working. I happened to look under my desk: mouse had become disconnected. Reconnected it and Voila, mouse action!!
Felt pretty stupid, let me tell ya.