Hello curtcain,
Congratulations on your new AirPort Express! It sounds like you are trying to extend your wireless network with your new AirPort Express, but you continue to get the error that your base station cannot be authenticated.
I recommend following the steps in the article below for the issue you described:
Wi-Fi base stations: Setting up and configuring an extended wireless network (802.11n)
http://support.apple.com/kb/HT4259
Thank you for using Apple Support Communities.
Best,
Sheila M.