Well, today we downloaded and installed firmware 1.7.0.274, and (while I hate to introduce more than one variable at a time) Makerbot for desktop 3.6.0.76. We are on our 4th (albeit small) build in a row with zero homing errors and zero filament jams. Knock on wood, we'll see how it goes, but this is better than we've sen since we started running this thing back in August. We've even entertained the idea of buying it off this guy, now we'll have to think about it even harder.