Sounds to me like your machines are infected with Malware of some sort.
We have AVG Busines Edition but I suppose anything is possible. Thanks for the suggestion. I'll look into it.
Well, that's what you get if you whack the F1 key over and over again... Troubleshooting stuff like this is extremely annoying over in Windows-land, mostly because there are so many places where this bizarro behavior could be introduced. Perhaps these two people have the same keyboard-management software installed? And no one else in the office does?