It is the circuit associated with our home office. However, the breaker never trips when the family is going strong in the office - two computers with speakers, lcd monitors, one multifunction network printer. Often will power down all the devices for the night and sometime in the middle of the night/early morning the breaker trips. I thnk it might be the multifunction? Even when off? I know many items draw power even when off. Would a surge protector with line conditioning help to prevent any electronics from drawing too much power or otherwise leading to a tripped breaker? At the least they would protect the items better! I am a bit stumped. It is a new home. Much thanks!!

I agree with Cynthia, hair dryers, microwave and toaster ovens are all suspect because they are only apt to be used in the morning. Middle of the night is a little puzzling however. Is there any electric heat in the house?

It is also possible that the breaker is defective but that's a long shot.