Connectivity issues since upgrading to Snow Leopard

Hello folks. Sorry to dredge up bad memories, but I upgraded my old MacBook Pro (2.5 GHz Intel Core 2 Duo) from 10.5.8 to 10.6.3. AirportX firmware update ran at the same time, now my network shows as connected, but I can't connect to mail or Internet. It was supposed to be an interim step so I could go to a more current o/s via online download, but obviously that's not an option right now.

The Airport is green, I show as having a connection to the network, but nothing works. I've restarted both MacBook and Airport, reinstalled SL, still nothing. There's no antivirus on board, and no sharing set up, which I gather were common issues back when the rest of you were encountering this issue back in 2009... Didn't occur to me it wouldn't have been patched long since.

Any suggestions?