Huge logout/guest theme problem

[Kamern]

This logout page decided to screw itself up and I have no idea how it happened, or where to fix it, I've never seen anything like it before. Could anyone give me a hand or point me in the right direction? It's strange, because for members, the theme is fine, but for guests, the rest of the forum is much like this.

[Marco van Herwaarden]

I doubt anyone can tell you based on only a screenshot.