Thanks for the reply, Dan.
I am going to put the bike up on the stand this weekend and give it another very close look. If I don't see anything obvious, I plan to take the wheel off and take the sprocket off and inspect the shift mechanism hoping to find something. It stands to reason that the noise comes from outside the hub because it changed so drastically by simply taking the wheel off and replacing it. But if nothing is obvious, I'll probably go to the 8-speed hub. If I do that, then I'll probably take a look inside the Alfine-11 and see what it looks like. I will post any interesting findings.
This just occurred to me: I can swap in the 8-speed wheel and *not* change the shifter... yet. The Nexus hub will be in its lowest gear, but I will be able to hear the noise if it's from any place but the hub.
Thanks again!
Steve