Yes, the update kind of messed up that dialog box. I cleared all the server caches to try to resolve this and checked suggested fixes on the website for the forum software, but that hasn't resolved this for everyone.
For me, using chrome, I was able to get things working right by clearing the browser cache and reloading the pages with the blown out message box 3 or 4 times. Once it is fixed, it appears to stay fixed, though if you fix this for the reply box, you might still hit it again in the new post box.