The Panopticon/Problems with Howling and Theory forums

I was just checking out Howling:The_Howling for the first time in a while when I noticed it wasn't working. The threads aren't appearing and there is something saying "Invalid tag extension name: forum" above it as well as some weird code. I looked in the archives for that forum next and saw it had a similar problem. Also, both the Theory forums and the Theory index page are also either showing the exact same problem or have weird code instead of saying Invalid tag. Refreshing the page and clearing my cache isn't helping. So, basically, what's going on and can it be fixed?