I was shooting Canon one time in the studio and I was perspiring heavily because of the subject matter (cough cough) and sweat got in the joystick thingy and rendered it inoperable.

The F5 should be sealed better than the consumer grade canon I was using at the time but I cleaned the contacts with just some blasts from an air can and I was back in business.

I was going to suggest some custom setting fix but it doesn't sound to apply in this case.