Facebook share problem

Hi,
I’m using socialize (but the same issue happens with all the share-something plugins) to share the posts with twitter, facebook and myspace.

The strange thing it’s when I press the socialize “share to facebook” button the share preview description is different for some posts.

Some are ok, with the description taken from the first lines of the article text. Others takes always the text from the about section.

And, the facebook preview image is always the first he find on the left column and users have to change it manually.

I’ve tried also to manually add some meta rel tags but nothing.

The website is http://www.rhymast.com

thanks
Andy