Can't reauthorize ADE on computer

I downloaded ADE for the first time yesterday.  Borrowed an ePub from overdrive before authorizing.  Realized my mistake; got an adobe ID, and authorized my computer.  Then I tried to return the Epub file (since I couldn't transfer it to another device, since I had borrowed it while "unauthorized.")  It would not let me return it.  So I DE authorized the computer to try to return it.  That didn't work either.  But when I tried to re-authorize my computer again, I got this error message: "You can only authorize this computer with an Adobe ID that has not been previously used to authorize any other computer or mobile devices.  Please try again."  This is weird for two reasons: 1) this is the only computer I've ever authorized, and 2) the note above says you can authorize up to 6 devices.  So, what to do?