I did a few (seemingly-simple) things at once:
1] Updated the forum to its latest version.
2] Added a new theme ("Thing").
3] Tried to have two domains share one IP (a common practice).
However, clearly I made some mistake, or there is some bug in the newest SMF software, or some buggy interaction, because (as many of you have emailed me to say) strange things have starting to happen.
So, I've reset a bunch of those things, and I encourage you (if you've visited the forum before) to clear your browser's data. Now, forum.truthcoin.info is the 'official' URL again, and hive-mind.info simply (independently) points to the same IP.
So everything should (?) be back and we can slowly walk forward.