Unusual characters in title breaks Facebook link preview

Facebook seems to choke on a couple of posts I’ve made recently:

• http://www.shadycharacters.co.uk/2013/07/miscellany-35-jay-z/
• http://www.shadycharacters.co.uk/2013/07/miscellany-34-what-th/

These are fairly typical of my posts, with the exception that they contain some unusual characters (Ћ and ±) in their titles. When pasting one of the problematic links above into Facebook, a preview of the link is not generated. Twitter doesn’t have the same problem. I’ve tried transforming the OG title with htmlspecialchars() (without any special arguments) but it didn’t seem to help. (Incidentally, I’ve been using the numero character [№] for a while now with no ill effects.)

Any ideas?

http://wordpress.org/plugins/opengraph/