Just bought a new iMac, and we're trying to connect to the internet through the ethernet port connected to a cable modem. We get an IP address assigned, but still can't reach the internet. Have spent hours on many calls with both Apple and Comcast tech support. All settings appear to be correct. We can connect using an XP machine, but both the iMac and a MacBook have the same problem - an IP address is obtained, but still can't reach internet.

Since we can get to the internet with the XP machine, the cable connection is obviously good, and Comcast says that points to an Apple problem. But we can ping the Comcast internet address, but no other address. Apple tech had us do a traceroute, and it showed the first connect to the Comcast IP address, and it goes nowhere from there. So he says this shows the settings and connection are fine, we're hitting the Comcast server like we should, but the problem is on the Comcast end since it won't branch out from there.

We took the MacBook to an Apple store, and it worked fine when hard-wired to their internet connection, so it's not a hardware (or, I would think a setup) issue. We also tried switching the cable modem, replacing the rented Terayon modem with a Motorola SB5101 we went out and purchased.

Network connections on both Apples show the following:
Status: Connected
Configure: Using DHCP
Valid IP address, subnet mask, router values are shown, as well DNS Server and Search Domain provided by Comcast.

Again, we've been through the settings many times with both Comcast and Apple tech support. This has become *extremely* frustrating trying to resolve. It must somehow be related to the Apple machines, since they both exhibit the exact same behavior and the XP laptop works fine, but what is it??? But what the Apple tech support says also makes sense... if internet requests are hitting the Comcast server, but not going anywhere from there, it would be a Comcast problem.