Can you temporarily install an internal ethernet network card and see if that will establish a connection online? If it does work, chances are it could be the ethernet port on the logic board. Other things you can try are:

-Deleting the Preferences file for the network.

-Zap the P-RAM (Command + Option + P + R). You may have to reset some settings afterwards, but this will generally correct most problems.

73s de Phreakout. :rambo: