I ask, because under Vista, when you set the leaderheads to high, it will change the rest of the games appearance...the quality is then lower, because the LHs would need DX11 and in the engine this one does not go with AA, so AA will automatically get deactivated, so that the rest looks ulgy...or so...er...there's a thread linked in the tech FAQ sticky, if you're interested, but i don't think that applies here.
But it still might be that there are somewhere conflicting settings...maybe there's anything set in the graphic driver directly?