Anyway, when you want to post a direct picture from Facebook you have to look for the actual image link, which is not the link you see on the navigation bar. Open the image you want from the album menu, and right click the image; then look for the link "See actual image" (or something like that, it's "Ver imagen" in my spanish firefox), then you'll access to the actual image with a link you can copy and paste without problems.
From this Facebook image:
http://www.facebook.com/u2santos?v=photos#!/photo.php?pid=2404058&op=1&o=global&view=global&subj=1151507990&id=1153591323
I got this link:
http://sphotos.ak.fbcdn.net/hphotos-ak-snc3/hs533.snc3/30266_1435642248411_1153591323_2404058_2250663_n.jpg
