I've had this problem for quite awhile and could never figure out what caused it but I'm assuming it's surely a coding problem. Anyone know how to get the Find a Username button to start working again in the private messaging?

Tried with firefox?

Yes, it doesn't work on any browser

Have you modified the templates? Or added any codes since the problem started?

Yea I did thats why I believe its a coding issue. I tried looking at the default template code to see if I could spot what's missing but I can't figure it out =\

Well, you might want to delete the published templates if its not too much of editing that has been done & you are aware of it all.