I'm wondering if perhaps some kind of dupe penalty.
When I signed up for Adwords, I made two copies of the index page and named them index_google1 and 2. Those are the pages I use for landing pages in the Adwords. None of them have links to them so I didn't think nothing of it. Except those pages are now in the index. The only way they could of been found is from adwords.
Now, I've excluded those two pages in the robots.txt file and also with metas on the pages themselves. I then did a re-inclusion request for good measure explaining what I thought had happend and what I did to correct it.