prl's dashboard

After 3 hours of fiddling around with all these suggestions - someone at Apple ACTUALLY fixed my problem.
I just got Time Warner, Arris modem - had the problem of not being able to connect to the internet though I could if I was connected directly to the modem via ethernet.
The FIX - was a complete power cycling of the modem, unplugging the power cord, REMOVING THE BATTERY, then upscrewing the coaxial cable.
I guess just undoing the power cord, leaves the power light on, which identifies that there is still a battery storing old information - blocking the assigning of an IP address to the airport express.
I waited 60 seconds, leaving the ethernet cable plugged into the AE, then screwed the coaxial back in, put the battery back in and then plugged in the power cord.
Now I'm back in business and so relieved. I hope this helps someone!
Cheers to all!