Using my second license did, indeed, get me into the game. But now I suppose I'll need to go through the
PISD unlicensing dance to get the locked one unlocked so that if it happens again I can do this sub-out thing.
I guess the Mac licensing thing isn't quite solved. The main thing, though, is to keep both licenses handy and make sure you hit PISD to unlock them as soon as you determine that one is locked.