I'm a builder, not an electrician, but the 009 only pulls 10 amps max and there are only two things that will cause a GFI breaker to trip: overload, i.e. too much current draw, and a short circuit, i.e. a wire somewhere in the 009 is touching something it should not touch.
Unless you have other things running on same circuit that are pushing current over breaker limit, it is likey reason #2. Do call CS. This is potentially serious.
Do you have a frigge or freezer on the same circuit? A lot of times electricians will wire an unfinished basement to an outside electrical outlet, since both require a GFI circuit. The fact your breaker didn't trip immediately makes me think it might be the compressor on a freezer cutting in that is actually tripping the breaker.
Good luck.