Hello,
Restarting your computer often solves this type of problem. But you are using an older version of Windows. Have you installed the latest Framework updates and other required software?
I think the problem is that you are using a game mod client. You can try disabling your Wow addons.
Can you in game select bugged mob, and go to tab "Tools" > click on the button "Development tools" > click on "Target info" and send me result please