A very small number of users who tried to join a guild during our earlier outages ended up in a corrupted state: they couldn't access the guilds they'd tried to join because the database and the guild service disagreed about whether they were actually members. We've now force-reloaded every guild across the cluster from the database, putting everything back in perfect sync with that squeaky-clean shine. This most likely didn't affect you: but if it did, you're welcome. You might need to refresh your client to get back in sync.