on your application account you should have received an alert telling you that the functionality of the API is going to change and you need to make the appropriate changes to your code.
The 'count' field was removed from the object. According to the documentation it was moved to the 'summary' section but it looks like they forgot to do so.
the only way i know to get the number of likes now is to go through all the like objects they give you (only 25 at a time) until you get to the end and count them youself.
edit
have a look at this post, aparently the 'summary' is within the 'likes' connection for the post object (i havent tried it)