it must have been something of that sort. i could see nothing obvious, so stood it on its side and gave it a few vigorous knocks, then blew a bunch of compressed air across everything, paying particular attention to both sides of the circuit boards. it works fine now, which is of course pleasing, but a little frustrating...saw nothing fall out, so is the offending whatever-it-was thing still lurking and biding time, waiting for another opportunity? in any case, thank you very much, as always.
