Don't know anything about American cars I'm afraid, but a common cause of this sort of thing is a courtesy light not switching off, usually one hidden away out of sight, perhaps the one in the boot, (trunk to you!), or the glovebox.
Also check that the alarm is not being triggered without you knowing it.
If this does not help, take it to an auto electrician who will probably fix it a lot cheaper than a dealer.
Good luck.
Lee, November 2007