Yep, it's exactly 6 times, and normally no beeps.

i think it IS the seatbelt. I've tried the ignition without the seat belt on, and get the same 6-beep sequence. that, after annoying neighbors with the alarm system, trying to figure out if the alarm was the culprit. of course, i can't repeat the problem any more. but, if it's just the seat belt sensor, then there's no real problem, i guess. could have been much worse

Thanks to all!