Just a quick answer (not tested anything because i am upgrading different sites, so unable).
So i can not give a solution, but try : it looks like this is a SEF url.
I do not know if FB can communicate through browsers with the server to 'read/interprit' the sef itself.
What happens if you use the full (plain) url; to the page itself ; INSTEAD of the sef ?(ht.../../.../ page.php?id=19 )
Hope it has some results..