I've never encountered something where a game copy will have errors if the original didn't have it already. I agree that a repair will fix a lot of problems, but my concern is that the repair utility has often reset the game version when I ran it, which meant that I had to install all of the updates again. If the guy doesn't have the patch files, it can take some time (and bandwidth, if he has an capped account) to download it again.
Haha Lucky you then! And thanks for also clearing up the 'repair reset' issue I forgot to mention.I also encountered the same thing not too long ago with a repair, because Blizzard decided to ''merge'' some patches together'' lol. Cost me 500mb of data, but in the end very much worth it, cause now I have every single patch (also backing them up on dvd's now lol). This wasn't the case when I lived in NZ and had 24mb/s dsl download speeds