Hi there,
Based on what you're describing it sounds most likely the electronics in those switches aren't working as expected anymore, the camera doesn't have any settings or functions which would lock those buttons. Due to the age of the camera it wouldn't be repaired anymore but there is an upgrade program for users with cameras that are no longer working. You can talk to Canon sales about the Canon upgrade Program 9am-9pm EST at (800)385-2155.
