Please note: this is not an attempt to get you to share a site I have been developing, there is a genuine issue with Facebook.
When I attempt to share a page on Facebook using their sharer.php script, it just doesn't do anything. You can see what I mean by going to http://www.vouchertastic.co.uk/ and clicking one of the "Tell your friends" buttons on the homepage - a popup of the Facebook sharer page will open but when you click share it just hangs.
Not all the "Tell your friends" buttons hang when I click Share. It seams like the working ones are those without the pound (£) character. Try to supress, escape or translate it and all will be fine ;)