ITunes Could Not Connect... (Invalid TCP checksum)

Question

I cannot connect to either the iTunes Music Store, access Gracenote CDDB, or stream from HTTP within the latest version of iTunes for Mac or Windows. These features used to work in earlier versions (although something else may have changed, as well). Most of the following testing was with the music-store component on a Mac, but the symptoms are the same for the other components and in Microsoft Windows.
The initial TCP connection succeeds, but I do not receive a response to any of the "GET" requests. Monitoring of the network traffic (using Ethereal) reveals that the TCP checksum is correct for the initial SYN/ACK (which succeeds) but invalid for the "GET" requests (which always fail).
If I manually connect to phobos.apple.com (using telnet from the same machine) and make the same request (i.e., identical HTTP headers), then I get the proper response. Note also that the TCP checksums are correct for every packet in this case.
All of the above leads me to believe that this is an iTunes bug. I would hypothesize that it works for others because there may exist an ambiguity in the checksum calculation and my network (and Ethereal) use one method while most network equipment (and iTunes) use another.
Powerbook G4   Mac OS X (10.4.3)  

Answer 1

PS: Is this the proper place to post technical-support questions? Do Apple employees frequent these forums? If not, where would I find the Email Support link for iTunes (like this one for the music store)? I can't seem to find the silly thing anywhere.