AOL is (in)famous for hijacking your settings when you run their installer disk.
Try this: Go to Network preferences and under the location pop-up see if the old location is still there, if so choose it.
If not, under the location popup choose new location and name it with a useful name like "Home Airport Connection".
Then under the show popup choose airport.
Then in the TCP/IP tab choose DHCP if it isnt already chosen.
Then click on the "apply now" button.
Hopefully that works for you.
If not, try shutting down cable modem, airport router and your computer. Then power on cable modem, wait 10 minutes, power on airport router, wait 10 minutes, lastly power on your computer.
Once you have the new location working properly, you can go to Network preferences and under the location pop up choose edit location. Highlight AOL, click on delete and then done.