Here is what has worked for me.
On the first start-up of iTunes after a reboot, make sure the iPod is not connected to the computer. If you have an iPhone, leave it connected. The iPhone is not affected by this bug. Once iTunes is launched, connect your iPod to the computer.
If you should forget to disconnect the iPod and do get the error message asking to authorize, just quit iTunes, restart iTunes, and then connect your iPod back to the computer, and all will be fine. You can then sync or do anything you'd like, and it should work fine,.
I suspect that something is wrong with the music lists in iTunes, and that some type of error message is generated with playlists that were created with earlier versions of iTunes. I also suspect that there is a bug somewhere in the iTunes software regarding connected iPods on start-up that automatically launch iTunes, and that's where the real bug lies. However, I am not a programmer, just a user.
Hope this helps. It's not a solution, but rather a workaround until Apple can solve the issue.