Who gave authorisation?
Q iTunes purchases play on my iPad and iPhone, but iTunes on my Mac tells me I must first authorise the computer. It then says I must deauthorise a computer to be within the limit of five, but my account says just one is authorised. Mark Venn
A If you have bought music from multiple iTunes accounts, each one will need to be authorised for that computer. Let’s assume that isn’t the case here and start by deauthorising all computers from the store account you’re using (Account > View Account > Deauthorise All). Log in to your Mac as an administrator, open iTunes and choose Account > Authorize This Computer. If that fails, delete the folder containing iTunes’ authorisation lists. In Finder, choose Go > Go to Folder and enter /Users/Shared/SC Info. Trash this folder, restart your Mac and you should be able to authorise the Mac.