Have you gone to Vergen and gotten the sword from Saskia yet? It's been a looooong time since I've played, but I remember you needed it (and that's the Hatred Symbolized quest, which doesn't seem to be completed in your quest list, though I'm not 100% sure it's marked right away). You have to go through this whole dark, monster-infested... mine, I think? You'd definitely remember if you've done it.

That's the only thing I can think of.

EDIT: I should probably elaborate that you're able to cross the mist to Vergen without getting rid of it altogether, and this is necessary. I remember there's a little magical light that you follow once you enter in order to safely make it to the other side.