We stumbled on a problem this morning. I won't go into gory details, but one of the moderators went on vacation, and it turns out he was the only one configured to see a subset of the topics. So none of the other moderators noticed. As a result, maybe 30 or so topics from new members were backed up without getting approved.
We found the problem this morning and fixed it. No messages were lost.
Apologies to anyone affected by the delay.