Is everyone still having problems in Houston? I definitely am -- I am here for a couple of months, renting an apartment that has TVMax as the ISP.
Here is the situation as I see it now -- periodically ITunes will work, but for the most part it is down.
TVMax subcontracts their ISP work to a company called Ignition Networks (866) 876-3278. I spent two hours on the phone with them on Monday. They have Port 443 blocked, which, if you look at this document
http://docs.info.apple.com/article.html?artnum=106439
you will see that 443 is the port that the SSL secure transaction data transverses. My guess is that the newer versions of ITunes use more and more data that requires SSL. I told the tech at Ignition that this was probably the problem and gave him the link to the above article. He said he would pass the article on to the network engineers, but would not commit to any other follow-up. He also said that they basically do not let their network engineers interact with customers.
So -- my advice to all you TVMax Houston folks who are going without your ITunes -- call Ignition up and raise heck with them about that port being closed. If enough folks call in and complain and mention taking their business elsewhere (say wireless cards or something like that) then they may actually do something.
I really do think it is a TVMax problem -- I have repaired keychains, repaired disk permissions, uninstalled and reinstalled ITunes and QuickTime, reconfigured my Airport and even tried direct connection to the cable modem. In some cases I got ITunes to work for a little while -- then it stopped again.
Please let me know if anyone makes a breakthrough. Good Luck.