I've just now returned from an overseas trip, and it looks like recently there's been some DNS issues which caused some issues for some people. For safety I temporarily disabled the forum while that was happening rather than risking users getting redirected to an unsavory third-party site. Sorry for the inconvenience! Hopefully this problem doesn't affect anyone else, I'm still chasing the root cause. Send me a PM if you see something wrong.
Longer term, I'm still hoping to build a new version of this forum; the current forum software is nigh on unmaintainable because of some historical changes that aren't easily fixed. I'll try to get that running in parallel without affecting the main forum, and hopefully it gives us a better way forward, but that won't be any time soon.