I'm using Bridge mode as well. Is there a way I can check from my system whether the modem and or router is using PPOE?
Oh, here's an odd thing. It changed. I just checked in my Airport Utility to see what my configuration was. I'm currently set to Network A, which usually means I can use my Time Capsule for backup. But it's now saying that it's not available. Hang on, let's see what it does when I switch to my own Network B...
OK, now the situation has completely flip-flopped. It is now able to see the Time Capsule, and is merrily doing a backup -- while I have my new Network B selected. I'm very confused.
Re-testing by switching back to Network A -- checking the Airport Utility -- and now both the Internet connection and the Airport Time Capsule icons have green "OK" lights.
Dangit, I think I have got the dreaded "intermittent" situation. But both setups look to be working now.
Well, I hope it was all just a false alarm. If the problem recurs I'll post again. :-/