Thank you for caring! It's working again.
Joking aside, I have found before, and I did again this time, that waiting until the kids are in bed and then having a beer or two makes it easier to put these things into perspective. (I am a recovering chocaholic so I have NOT been taking all that advice about referring the matter to Mr Cadbury!!!)
I'm sure the general advice is not to drink and sew, but once I had that mental space between me and the cold hard reality that my machine is a mad creature who hates me, I was more able to thread, rethread, unscrew, dust and (I think this might have been the best bit) hold the entire thing upside down and shake it in case anything was going to fall out from in there. (Yes, I was sitting by a large picture window as I did this- I can thank Mr Guinness for the fact that I did not follow through on the obvious temptation.)
I peered in as I turned the wheel by hand and watched out for microscopic particles. But I still think it was the bobbin race. Either way, after the gazillionth adjustment, it is working again, for the moment. But I have its number, and just as soon as I win lotto I am replacing it- my girls can learn on it- that'll teach it a thing or two!