I am having a problem viewing levels of other characters in the game. Instead of levels I see a message stating something like helplessly vulnerable or moderately vulnerable, or equally matched what ever the class is. I would like to know which addon is causing this and how to disable it.

I think we'd need more information than that, What addons are you running, When did it occur, What addons were installed on that day.

I have atlas, atlasloot, cartographer, curseprofiler 2.0, all the boss mods, extra bars, gatherer, myroleplay, omen threat meter, and questhelper.  At the time I only had atlas, atlasloot, cartographer, curseprofiler 2.0, the boss mods, gatherer, myroleplay, and questhelper active. I disabled them all and it was still showing the messages instead of the levels. I need help.

i just downloaded the burning crusade and now questhelper is gone and i cannot download it off curseclient or curse.com so im not sure what to do right now