I just did a Facebook like on the home page and it picked it up fine, so new clicks are being picked up, as you mentioned.
If the URLs themselves have not been changed either before or after you upgraded, then I am not sure what the issue is. The only thing I can think of is that you might have some posts under more than one category and that the new upgrade is picking up one of the two categories in the URL that the post was not originally submitted to.
I had this issue with a client site of mine, after upgrading. It had originally posted stories to Category X, but the new upgrade was then submitting them to Category Y and I had install a new plugin that let her manually tell which category should be the one WordPress used as the default.
I would suggest submitting this issue to the Sociable support page. I myself have nothing to do with this plugin, but have offered support to some people as I have worked with it a fair amount of the past two years.