Problem with Google is that it is hit and miss and they never tell the rules up front. If your links are not any good and those back links are not what Google classes as relevant , then you will be blacklisted and not indexed. You need to email the local Google centre with a re-inclusion request. They do not have to and they sometimes don't.
Make sure your links are with sites that have good links and ranking. Pro Dive has 12 full time staff working on the site and
SEO, plus we spend around £300,000 PA just on keyword and ADWORD advertising and still we sometimes find ourselves out ranked by lesser known sites.
It's a dark art!!!!!!