I'm guessing you have a shoulder mobility restriction. try some aggressive shoudler stretching to root it out. I've also noticed often when people start snatching their shoulder is out of the socket, or it's in at the top but pops back out on the way down. Go back to your swings and see if your shoulders are tight, lats firing, or if they're kind of being pulled forward.
I think seeing an RKC would help with a lot of this stuff. Or buying a really good DVD.
