Viggo,
There are multiple og:url (and other) tags on that page. If you open the HTML, you'll see 2 sets of tags. The first group is not from JFBConnect, the 2nd group is. Having 2 sets is bad, as you can see from the debug tool.
As for articles without images, I'd recommend setting a "Default" image in the Open Graph area of JFBConnect, like:
image=http://site.com/link-to-logo.jpg
Whatever you put there will be the 'fallback' image for all your pages, incase an image isn't specified.
Finally, on pages without an image, you can still use the {SCOpenGraph image=http://site.com/image-for-article.jpg} tag to specify an image for that page, even if the article doesn't have that image.
Hope that helps,
Alex