Network problem

I was hoping someone could help me with a DSL problem.  I was on Earthlink and switched to SBCGlobal last night.  The installation worked fine, but everytime I turn my computer off and turn it back on it won't work anymore.  I have the settings on "obtain IP address automatically" and "obtain DNS server address automatically".  The only way I can get the internet connection to work is to type in specific IP and DNS addresses, then go BACK to "obtain automatically" on both.  Then it works fine, but I have to do this every time.

I talked to a SBCGlobal tech.  He told me to go to the ipconfig prompt and type ipconfig/ renew, and I got an error message that a file was missing.  The tech told me the problem was in my card and that I'd have to reinstall it, but I tried doing that and it didn't work.  I tried using the Dell Dimension ResourceCD but it didn't help and just said it didn't have any updated info.  Anyone ever have a problem like this?  Thanks...