Originally Posted by Digitalgas
Full window Attachment Manager

It looks like you have a broken 3rd party javascript breaking your forum.

Check that all your custom add-ons are up to date, and not broken. Once you fix that, all the rest of the javascripts on your pages will resume functioning correctly.

We discussed this when I replied to your exact same question last week at:

Current developer of UBB.threads PHP Forum Software // 7.7.4 released!
isaac @ id242.com // my forum @ CelicaHobby.com