I've seen alot of people complaining about the 'Red Text Spam' in the middle-top of their screen, saying stuff like 'Ability not ready yet' and 'Out of range' and such. So I found this addon that removes the text and I'll just post it... http://www.wowinterface.com/download...69-CError.html
http://www.mmo-champion.com/interface-macros/(list)-commonly-used-addons/ Just report the addon there and it will be listed. Anyways, the most common one is ErrorMonster, not sure if it's discontinued though.