I am running Windows 7 and have been using iTunes on this computer for about two years. About two weeks ago, all of the songs I have purchased from iTunes (a few hundred) could not be played because this computer is no longer authorized for some reason. When I check my account, there is only one computer authorized to play the songs, which is the computer I am on.
Whenever I start up iTunes, it says that "This computer is no longer authorized to play purchased items that are on the iPod "Victor's iPod". Would you like to authorize this computer for items purchased from the iTunes Store?" I, of course, try to authorize it, but after entering my username and password (both of which I am completely certain is correct), I get the message "We could not complete your iTunes store request. An unknown error occurred (-42408)."
I have tried every day for the last two weeks using four different Internet connections. Once, and only once, I actually didn't get that message, so I thought my problems had disappeared. However, the next time I plugged in my iPod and started up iTunes again, the same issue returned.
I have spent at least four hours searching for answers in this forum and on Google.com, and have tried approximately 14 suggestions, from minor ones to major ones. Unfortunately, it looks like there are thousands of people with this exact same issue, and although some suggestions have worked for some, a lot of people are still experiencing problems.