Did talk to my ISP (at least the tech guy who was on call on a friday night!) - and his take was that the problem is "off network", that they have no way to control the route path between two points on the net, and that it's up to the internet to take care of itself - when those efficiency algorithms work out that there is a problem, I guess. Don't know enough to say whether or not that's true.
Frustrating thing is that this means the game is just not available to me, that I can't play on line until something magically fixes itself. Are these routes handled someplace in the architecture of the internet, or are they recorded somehow in my router? (wishful thinking, I know). I wish there was a way to clear some routing cache or something...at least then there would be something I could DO.