Can't Connect to Internet

[TN6vols]

I recently purchased a Samsung Captivate. When I tried to go onto the internet the username and password prompt showed. The username was the person that I purchased the phone from. I done a factory reset and entered my account as the default account on this phone. Now I can't connect to the internet or use the Market. I also use AirVoice for my service. Anyone have any ideas as to what is wrong?