iTunes will not authorize my computer. It is the only computer that I am trying to authorize, I can buy music, movies and apps through the iTunes store and they all download fine. iTunes says that I am logged into my account and allows me to purchase media from the store. When I try to play a movie or song or try to sync an app to my iPod Touch it tells me that my computer is not authorized to play that media. When I go to authorize my computer it gives me the following error message: "There was an error storing your authorization information on this computer. The required directory was not found or has a permissions error. Correct this permissions problem and try again, or deauthorize this computer if the permissions cannont be changed." I have de-authorized and authorized my computer several times. I have tried completely logging out of the iTunes store and then logging back in. I have tried restarting my computer. I checked the permissions of [Home Folder]>Music>iTunes and its subfolders and they all seem normal. I am out of ideas. Help!