I've had this problem for 2 weeks. Google is not showing the star rating of my post in searches, although in the test snippets tool it's showing correctly. Google is also crawling the richsnippets‎ values since I specifically fetch a post with the Google Web Master Tool and check the values.
Here is what it looks like in Google snippet tool result:
and what it currently looks like on Google:
I'm using the GD star rating plugin (1.9.22) and Wordpress (3.5.1).
Have you looked in Webmaster tools under Search Appearance > Structured Data
It will list any data there that it considers important. It is worth noting that they tend to be a bti funny about reviews, if you have less than 10 reviews don't expect anything to show. Also structured data is notoriously up and down, it isn't and exact science so maybe give it a little longer.