I m have HUGE mouse lag when playing wow. and it does it for my whole computer. I cant even play WoW anymore because of it. i have razor naga. Radeon HD 6800 , and a custom built computer. I have never had this problem. I got rid of all my addons, and then deleted cache folder, WTF folder. Nothing worked. Then i deleted WoW all together reinstalled. It worked for a couple of hours, and now its back to being where my mouse is super laggy.
I am having the same problem and trying to fix it now. Only started happening this week.