Argh, it looks like I never really got OG working properly. The Hive Group has lots of posts (especially its forum), but the Group page says: "No posts in this group". I'm pretty sure that's just plain wrong.
In case it was just something about og_forum that was broken, I also tried adding a "page" for the codeparse group, but it didn't work either.
Help, I'm going crazy!
Searching drupal.org now...
Grumble
I had to enable "access control" in the OG module in order to get "posts for this group" to appear on the Group page. That just doesn't seem right. Oh well.