Is the room screwing up the PC?

We had someone who was having problems with her computer…mouse wasn’t tracking right, locking up, etc. She quit (not because of the computer!). Someone else moved into that office, and took her computer with her. Her computer used to work fine, now has the same symptoms (mouse slows down, freezes, computer freezes for several seconds, random lock-ups, etc.). Could it be the room? One corner of the office is a closet that contains our phone equipment and two servers, but the server seems fine. I’m at a loss. Anybody run into anything like this before? It’s a law firm, not a nuclear power plant!