I upgraded my test board, where I updated my style for the live site. Everything worked fine and continues to work fine there. I upgraded the live board, and imported the updated style. I have made 2 addons that make use of the forum_list sidebar hooks.
One is a block containing 5 items from the recent activity stream, the other just includes a template with adsense. On the live board, the Recent Activity block stopped updating (though the stream did on the actual recent activity page). It continues to work fine on the test board.
I disabled and re-enabled both of the add ons. The Recent Activity block disappeared when I disabled it and refuses to come back when I enable it. The Adsense block doesn't even disappear when disabled.
The forum_list template is stock. I am not sure what could be causing this, any suggestions as to debugging are welcome. I have not done much since I can only reproduce this on my live board, which I did not want to take back down at the moment.