Thanks very much for the thorough info guys.
Kenchan, I replaced the battery with an Optima Yellow Top when this happened the first time, and it happened again within 2 months after that, so I'd assume it's not the battery itself that's the problem.
Mults, I'd been thinking #3 is the answer... but does this evidence give me a legit warranty issue to go to the dealer with? I'm unfortunately not as laissez faire as you seem to be
especially considering I've had more issues with this Z than I've had with my past 3 Acuras combined.