Hi Kris,
I know it has nothing to do with IE, because even I run the editor in Google Chrome, it shows the message box as well, but Safari works fine. I am looking forward to your GA release, hopefully it does not take too long :) , we will need it soon.
So far, I really like the web editor, I think it is the best web based business process designer.
Thanks for all your hard work and make it happen.