Never heard of this. I have, however, had some of the saves I've made corrupted. I turned on ubersampling which destroyed my frame rate, and I noticed that saves made when the frame rate was especially low (~17 FPS) were hit-and-miss on whether or not they'd actually be recognized. The saves appeared in the save folder, but the game wouldn't actually recognize a number of them. That's really the closest thing I've ever even heard of, but never something that destroyed all the saves. Are there files in your save folder? I suppose it's possible that it's some kind of corruption, but I can't recall ever hearing of something like that.

Where were you at in the game? I have a number of saves at various points from both paths in the game, and while it's hardly ideal, it could at least lessen the amount of content you have to play through again. A number of them are unleveled, so you could still theoretically specialize in whatever skill tree you want, if you're interested.

Were you switching between running as admin and not running as admin? When you don't run as admin your save games may be redirected to a different location, although that usually happens for older games rather then recent ones like The Witcher 2. Try running as admin and not running as admin and see if the saves reappear when using one of those options.

Also, just to check: you have been able to load saves correctly before this, right? This wasn't your first time trying to load a game?

I have the same problem :S And I ready to leave Flotsam. I've downloaden my copy form GOG :S
but I found them in User/Doucments/Witcher 2/ gamesaves, yet somehow the game doesn't see them . We are talking about quicksaves