Not authorized Already authorized What's the deal

Syncing my iPad I get, 'Some of the items in the iTunes library, including "White Rabbit", were not copied to the iPad "Sam's iPad" becasue you are not authorized for them on this computer. Go to Store > Authorize This Computer.'

When I do that I get, 'This computer is already authorized. Including this one, you have authorized 2 computer out of your available 5.'

I've been going around and around with this for years. I deleted iTunes from my Mac, swore I would never use it again and resigned to never listening to the songs I purchased. But now I have a new iPad and it uses iTunes to transfer files (go figure).

Besides driving over to 1 Infinity Loop and throwing furniture through the windows what should I do?

Thanks,

Sam