You can only have ONE device trying to do PPPoE. It looks like your computer is trying to do it through your AEBS. That will only cause the problem you're seeing. Changing your Mac's settings may not have "taken," so I suggest you delete the location you're using and start fresh. With no location, the Mac should default to being a LAN client-which is what you want-when you try connecting it to the AEBS again. For what it's worth, I use SBC DSL and my router has handled my connection from the begining, so I know it's both possible and easy if everything cooperates.
I'd also try connecting through a cable. If it works with the cable but not wireless, you may have some other issue going on.
Oh, and WELCOME to the MacNN Forums!