Configuring a new router

[#1]

I have an ASUS RT-N12 router running DD-WRT and a zoomtel ADSL modem. I can't get online with them, and I don't know what I am doing wrong. Does anyone know if these are compatible products?
The instructions for getting online say PPPoA but my router only does PPPoE, which I believe is normal because it's the actual modem that should be bridging it. Are there any other settings I need to put, other than my username/password?

[#2]

Going nuts here Tried the modem directly into pc and setting up pppoe but get Error 651 - Your modem has reported an error
Anyone got any advice at all?