Recently I had a problem getting Fedora 7 to work with a DSL modem provided by ATT. The browser kept saying “looking up whatever.com”, like 15 seconds before starting to look for the page. The ethernet adapter was properly installed. The solution was to remove the “Automatically obtain DNS from provider” option in the Network applet, then RESTART THE COMPUTER (for the change to be permanent), and then put instead
from opendns.com as primary and secondary DNS. Then RESTART AGAIN. Now it works the way it should.