Definitely an issue but I think it was caused by the recent forum software update. I've been looking thought the templates to see if it was something I broke but I can't see what's wrong.
Edit:
Okay, so it took some doing but I figured it out. Apparently, they updated the CSS for those overlay boxes but the change didn't work its way into the custom themes. I just updated it and it should be working but you'll need to clear your cache in order to see it.
Edit:
Okay, so it took some doing but I figured it out. Apparently, they updated the CSS for those overlay boxes but the change didn't work its way into the custom themes. I just updated it and it should be working but you'll need to clear your cache in order to see it.