Error message -42408--computer not authorized

Question

I upgraded my iphone software and now when i connect my ipod, the computer is no longer authorized. when i try and authorize i get message "We could not copmoete your itunes store request. an unknown error occured (-42408). There was an error in the itunes store. Please try again later."
I have tried for 2 days, including "fixes" offered by itunes support to no avail.

Answer 1

I'm having the same problem with iTunes 9.0.3 and my 2nd Gen Nano (running 1.1.3).
The problem is with the few (5) protected tracks that I have left in my library (m4p files that have not been offerred as iTunes Plus upgrades). I do not know exactly when the problem started; my Nano syncs to a smart playlist that rotates its contents on the basis of what has not played recently; it may have started anytime within the last 2-6 weeks, and I first noticed the problem one week ago.
The problem started once these files were rotated onto the Nano: after they had been moved onto the Nano originally, upon each subsequent sync, when the Nano and iTunes connect to each other, iTunes tells me, even though my computer is authorized, that
"This computer is no longer authorized to play purchased items that are on the iPod. Would you like to authorize this computer for items puchased from the iTunes store?"
I click the "Authorize" button and, for the most part (at least for the first few days), iTunes would allow me to enter my password and then tell me that the computer was already authorized. Then, today, I too began getting the special -42408 message that loops me back to the original prompt.
I have no problems playing the m4p files on the Nano or on iTunes. So long as I can get it out of the 42408 loop that sends me back to the "Authorize" or not menu, the Nano will sync fine. Moreover, the same files will sync and play without any problems whatsoever to my iPhone 3G (3.1.3).
I have seen the relevant help article at I have seen the relevant help article at
http://support.apple.com/kb/TS1389
and have tried all it suggests, but nothing has helped the problem.
iTunes Store Customer Support advised me to deauthorize iTunes, delete iTunes Helper, delete iTunes, reinstall, and go, but this did nothing.
I did deauthorize and reauthorize iTunes about two weeks ago for an unrelated reason, and I do wonder if that could have triggered something. Again, I can't be certain, but this problem seems to have started after 9.0.3.