Why am I getting "Not Authorized" then when I sign in I get "This computer is already authorized"

Hello,

I migrated from Snow Leopard to Mountain Lion on my new iMac.  Why when I down load using iTunes 11.0.2  I get the following loop of windows:

       I click Authorize

       I enter my Apple ID and Password

     I click OK

Then then after a couple of seconds the windows repeat again from "This computer is already authorized ..."

Please Help!  Getting very frustrating!  Long time Apple customer since 1985.  This is the worst exsperience I have ever had with Apple products!

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