I bought a new iMac. When I plug my iPhone into the iMac, iTunes recognizes the iPhone, but I can't add or delete song or anything for that matter. I'm signed into iTunes and everything. I can transfer purchases from the iPhone, which is odd. But I want to edit my playlists and delete some stuff. My old computer the iPhone was linked to is an iBook G4. Is there something I have to do on that computer?