Something interesting happened to me today. My RSS feed was broken with some invalid chars half of the day. During that same time I noticed that google was not returning any results for any of my keywords. Even rank 1 keywords. However it did return results with the site: query so I know I'm not in the sandbox. I fixed my RSS feed, then I check my google rankings later and everything was back to normal. Coincidence? This is just a typical WP blog.