"You are not allowed to perform that action!"

Okay, so everyone on my server seems to be getting this message that is not an admin. I'm not quite sure what is causing it as the console shows no plugin activity. This wasn't happening yesterday and I have not added, removed, or edited plugins since. Any ideas as to what is causing it?

Woops, I found the issue; Antigrief updated and that is the cause. If someone can delete this thread, that would be great

EDIT by Moderator: merged posts, please use the edit button instead of double posting.