It's not a game-breaker, I can tell you that much. It's probably a loophole in a quest line, or some kind of exploit someone found. I don't have an internet connection my PS3 can use, so I guess I'll find out the hard way if this bug just ruins the game in every way, making it a waste of time and money to play, or even think about. It's strange to me that someone can devalue an entire game because of a single error.
It'd be like dismissing Beethoven entirely because a recently discovered symphony of his had a movement that wasn't related to the others at all.