Computer won’t start…UNLESS…

I have a computer at work that will not start unless you have a mouse plugged into the ps/2 port. It normally uses internal bluetooth wireless mouse and keyboard. These both work fine when the computer is booted using another mouse.
The computer is a Gateway profile 5.5. Is there a possibility of a short in the mouse port? We had a few power outtages yesterday and this seemed to have caused the system to malfunction. Thank you.