I've got a Buffalo WCR-1166DS, I was able to flash the OpenWRT firmware on it and was able to set up both PPPOeE and wireless. Everything was working just fine. But playing around with the settings a bunch to get a feel for how things work, all of a sudden I could no longer connect to my ISP with PPPoE. I reset the firmware bit that didn't help either. The connection works just fine with the old router (Airport Express) but as soon as I even connect the Buffalo router with OpenWRT the PPPoE connection fails on the Airport Express.
Is it possible the ISP somehow is blocking the Buffalo router now because of misconfiguration or something along those lines?