I'm not sure if this is a bug or not to be honest, but it seems to be. If you look at this issue in the Edit module queue, as I understand it there is a problem with the Omega theme printing things where it shouldn't, or at least where the Edit module doesn't expect it.
I tried modifying node.tpl.php with the recommendation in the post, and it seems to work ok.
Is this something that could be fixed?
My apologies for my deep ignorance of things theming, I'm only just getting started with Omega