Aftermarket deck won't shut off

[Kingpin]

The strangest thing happened last night...

I've had my 2003 Alero GLS for 3 years now and installed an aftermarket deck right after I bought it.

Last night, at 3:30 am, my wife and I heard music coming from outside. We were wondering who could be out there with such loud music at that time. A few minutes later, my neighbor was pounding on my door demanding I turn down the noise. It turns out it was my car!

I don't know how this is even possible. When the keys are not in the ignition, power to the deck is cut as soon as you open the door. But now it won't shut the power off.

I've been lurking around these forums for a while now and I'd appreciate knowing if anyone else has had this happen. I used the search feature and didn't come up with anything. I'd appreciate any suggestions.

EDIT: One piece of info I neglected to record earlier... I had the car in for detailing yesterday and they cleaned it inside and out (and the engine). It looks great but the carpets are still wet. Could there be moisture building up in the data bus adaptor?