If you can't pint the yahoo domain (i.e. www.yahoo.com), just the IP address they provided, then it sounds like your DNS configuration is wrong.
I don't know if SBC uses special software or not, so the best I can do is look at any setup guide sheet they may have sent you and repeat the steps for the DNS settings.
I have a Windows XP service pack 1 system. I babysat our niece a while back and after she left I couldn't get on to the internet anymore. I spent hours on the phone with SBC Yahoo, my internet provider. ( I have DSL ) I know very little about the technical stuff of computers, but the following is what I was told.
I got a public IP address twice
I can PING Yahoo IP, NOT DSN ( domain server)
and was told it was a software confilict and that SBC couldn't help me. I don't know what to do or how to fix it. Any help or ideas would be great. I called around and most places will charge me, but won't guarnette that they'll fix it. Sorry I can't spell very well today. thank you all.