Let me clarify a few points:
1. The Witcher 3: Wild Hunt is an amazing game. It really is.
2. I have no interest in bashing the developer because of what appears to be an isolated and very rare incident.
That being said, I think we all have to accept that CD Projekt Red's game is simply too unstable and probably wasn't ready to launch. I also have a responsibility to my fellow gamers; I want to warn them in case they encounter the same issue. Now, I haven't been able to find evidence of this game-ending bug anywhere online (and trust me, I looked) and therefore, I have to assume I'm in the extreme minority.
Even so, if it can happen to me, I'm sure it can happen to someone else. Here's the scenario:
After you kill the Griffin in White Orchard and claim your prize, you're supposed to return to Vesemir and prepare to leave this opening introductory area. This is the last part of the Lilac and Gooseberries mission. What's supposed to happen is that you'll find Vesemir in the tavern, after which a brawl breaks out and you take off. The only reason I know this is because I had to look it up.
What happened to me is that after killing the Griffin, Vesemir is standing outside the tavern again. The main mission marker is right on him but he only repeats the same dialogue lines from before and nothing happens. Inside the tavern, it's a strange scene. There are some bandits there; some standing, some sitting, and if you talk to them, they respond with shouts and yells that imply they're in combat. Vesemir is still standing outside. And that's it. The game is stuck.
Un-installing and re-installing the game data does nothing, and neither does returning to a previous save file (guess I didn't have one that went back far enough). Now I have no choice; I have to start over. Word of warning: Before you talk to Vesemir to trigger the Griffin encounter, create a Manual Save and DON'T overwrite it after killing the Griffin. Maybe, if the game does break after, you can return to the save before the fight and try again. I don't know; it's just an idea.
This will delay my review indefinitely and I haven't decided yet what sort of impact this incident should have on the score.
Related Game(s): The Witcher 3: Wild Hunt