Help! I synced my iphone4 to a window PC before i get a mac recently. So, when i try to sync my iphone 4 to mac. I was told that "the iphone cannot be synced. You do not have the privilege to make changes". 1. i clicked store> authorize this computer. =failed. 2. restart mac. =failed. 3. reinstalled itunes. = failed. 4. restored iphone4. =failed. So, what else can i do? is there any solution?