Ok, If your problem has been resolved, then disregard. I had this same share problem today and I resolved it. First I disabled any Facebook share plugins I had. Then I deleted my OWN entry into the contest to set the URL.
OK, then I tried again and entered the contest first to set the URL and then my sharing options for Facebook worked!
Hope that helps. Also, don’t have your contest on your page set to PRIVATE when you test it. It has to actually be LIVE!!!! I know it’s a drag but it will not share.
flgirl, thank you for answering and your time to explain me what you did to solve the bug.
Unfortunately, days gone by, and I couldn’t let the buggy plugin online, so I uninstalled it, therefore you cannot see it in the link. I found another way to do what I needed, too bad for the plugin creator.