I have an odd problem with one of my users - when he toggles an F key item on or off (Ortho, Osnap, etc.) the toggle does not engage until he moves his mouse.
Let me try and give a more visual picture. He hits the F3 button and, for most of us, if you are looking at your toggle bar at below your command line, you would see the Osnap button engage/disengage. His does not. Until he put his hand on his mouse and moves it in anyway - then, all of a sudden, you will see the toggle button engage/disengage. It's one of the strangest things I've seen, and I haven't been able to find any other remarks on this issue.