I once worked Tech Support for a point of sale software package. There was really no internal help desk, so we got all of those questions as well.

One day our front receptionist that her computer is being really weird and she can't type - it keeps inserting 3s in the middle of what she is typing.

I take the short walk down the hall to her desk and see that, indeed, a never ending string of 3s is being input to her screen.

"I can't figure out what's wrong." she says.

Then I reach over and remove the edge of an open binder whose edge was resting on the 3 key and enter key on the num pad.

"That should fix it."

Walked back to my desk.