I tested a few pages on your site and the errors seem accurate. If I reload the same page repeatedly, sometimes I get a blank white page. In the Debug Tool, if I hit the Scrape Again button, it usually loads the page the next time.
For the "More than one OG URL tag specified", that's accurate as well. If you look at the HTML of the page and search for "og:url" you'll see it's in there twice. There's a group of og tags right at the top of the page. Those are not put there by JFBConnect but are conflicting with the tags we set. You'll need to determine what other extension is setting those tags on your site and disable them.
I hope that helps,
Alex