[patrickb]

basically, either run the Rebuild Forum Information in Maintenance->Update counters.

What this calls is basically build_forum_permissions....which in turns calls build_forum_genealogy....which updates the genealogy of your forums (specifically the childlist and parentlist fields) which are necessary to show up in vB.

I have an external interface to add forums to my vB site. I also have a cron job that runs every hour to see if there's any new forums added. If so, it calls build_forum_permissions to update everything.

Hope this helps.