We've been having some issues with a bug in the auto-ban system (designed to prevent people from resetting their DSis), which would also handle IP bans. There was an issue in which regular people were getting banned for an unknown reason (at random). I think it may have something to do with Hatena returning incorrect Flipnote Studio IDs for sessions.
I've gone through the moderator log and found all the manual bans/blocks, unblocked all users, and reblocked all the ones we've issued manually. If you have any further issues, please comment here or message firstname.lastname@example.org.
Thanks, and sorry for the inconveniences you've experienced.