Windows XP and DSL connection (err.678)

Hello:

I just built a new PC (P4 1.4ghz, 384mb Ram, and WIN XP). I also have DSL from EarthLink. I used the connection wizard (several times) to try and connect to my DSL account. I always recieve error code 678. I have replaced my NIC twice,and have been going round and round with EarthLink Tech Support for over 2 weeks now. Does anyone know how to resolve and error 678? The modem lights are all green, green, green.

Please Help!

Thank-you