The blog was hacked: some arsewipe had figured out how to use it to host a bunch of links to dodgy sports videos, and in the process they messed up the permissions on the directory housing the scripts that run the blog.
All cleaned up now, everything back online. Free bonus extra: Markdown should be working in comments as well as basic HTML tags.
I plan to throw in some really major changes on the blog in the not too distant future—between April and September next year. (Hint: new and much faster server (this one is a 2008-spec machine), new blog engine, design overhaul, possibly a separate conferencing system—but right now I have other things on my plate.