I had this problem with no addons at all sitting in an empty exodar the day the patch came out ... had to change my graphic settings to fix it. Well, my brother changed teh windows side of things and I set the in game graphics from ultra down to fair.
I now have nUI as well as about 20 other addons and in a lively stormwind running at 50fps along with a bugged addon (TauntMaster in this case )erroring out every 60 seconds making the fps worse
