I am having the same problem lately with a few sites. Out of the last 50 sites I have built I think 4(1 Amazon store and 3 micro niche sites of 1 has 3 crappy articles and 5 good articles the other are 4 articles) of them have not indexed. They are not all hosted the same place or using the same registar. I have tried various things on them in different combos including types of link building, submitting to webmaster tools, adding fresh content from the last time it was crawled, pinging, etc.. They are indexed in other search engines, the only issue is with google. I am going to change the theme on one of them today and resubmit it. Running out of ideas here as I see nothing wrong with these sites.