I figured I would stop lurking and come out to interact here. I am in the same boat with many of you. I did my PFI in July through Position Tech and had first page rankings on MSN with the optimized pages I included in my PFI. I disappeared around the first week of October. I have tried re-doing my SEO, changed the URL, and I have had no luck.
Now I'm guessing you either stuffed the keywords section with keywords that were not visible on the landing page, or whoever generated your XML document did something illegit/shady.