To follow up to answers: no real problems with transmission stuff since the early jerking at high speeds ended at around 28K. It had been making a groaning noise from the steering column at takeoff and in turns. Mechanics found it, but didn't have Help Desk solution on the Saturday I had the car in. But transmission? No. No jerking, bumping, etc, just "stop".

Mileage has hung steady at 38 with mixed highway around town trips. I'm in coastal Georgia, so don't think the cold did it. As to the flush, I just had the very expensive 90K service done a month ago, surely if something needed addressed, they could have done it then? Although come to think ofit, the warning light did come on fora few days after their service. When I called, they thought it was likely the old gas cap bugaboo, sure enough it blinked out a few days later. Now I wonder?

Ideas, theories, suggestions are all welcome!