Only thing I can think of that changed in the blog or in mojoportal in general is that we upgraded to newer versions of jQuery and jQueryUI
but this is controllable from Web.config
<add key="GoogleCDNjQueryVersion" value="1.5.2"/>
<add key="GoogleCDNjQueryUIVersion" value="1.8.11"/>
if you want to try it you could change jquery back to 1.4.2 and jqueryui back to 1.8.6 and see if that makes any difference.
Really I don't see how page contents or javascript used in the page should prevent Facebook from linking to a page it still has to be a facebook bug in my opinion, a link is a link and that should be the end of the story, a link is not a complicated thing.
The only way to go back is if you have a backup of your web site files and the database from just before you upgraded, you could restore your site.
Best,
Joe