http://i.imgur.com/p3JdK.jpg the one above my unitframes, i use my own and want to disable it, it popped up a few days ago when i updated addons for new patch. ty!
You can find out by mousing over the offending element and using; /script DEFAULT_CHAT_FRAME:AddMessage( GetMouseFocus():GetName() ); This should pop the name of the UI element in your chat window, which usually gives it away.
Or use /fstack.