Good grief. I just got a Scarlett 8i6 as something with more IO than a Mobile Pre and didn't cost a fortune like an Mbox, and I was having this weirdo issue in Pro Tools 10. Thanks for the guide at the top of this page, it solved it. Not sure if it's Focusrite's problem or Avid's, but yeeeeeeeeeeeeeeeeeeeeeeeeeeesh.