This is a typical error where the game tries to access a file and fails to find it or doesn’t have access to it. As you mentioned, unpacking the game for the second time fixed this problem. I can only assume the zip pack didn’t finish downloading when you started unziping it for the first time, or you didn’t wait for the extraction process to finish before running the game. Just don't rush it and this is the solution.
Oh, and you don’t need to lose any progress from the first playthrough. Just copy the entire save folder into the new version and proceed from the last save point.