I had to change some permissions around so that some users would be able to modify templates. All users should have at least read access to all templates. I just tried to move my item through the workflow but I'm getting this error now.
I've tried moving it through the workflow via a user with admin rights, and they don't get this warning, so I assume it's a permission issue, but the question is, what permission access is causing this, I've never seen this message before.