Yes, the same thing happened to me. Now if only I could think back and remember what I did ...
I think first I tried renaming the game file, and that didn't work.
Then I think what the problem was, was that the installer and the game were on different partitions -- apparently the installer looks only on its own partition. I dragged the installer onto the same partition as the game, and then ran it. Then it worked.
I could be remembering wrong. Let me know if this works or not.
Need... sleep...