hmm... ok, i located the problem!
i was able to access posts in the forum, by typing in their url -- just not able to access the forum, itself.
so, i stumbled across the problem -- it appears unregistered users posted on my forum! meaning someone who registered a few months ago, that i deleted a few months ago, just came back into the life of my forums, posted, and messed everything up!
his name appeared in alligator brackets
um... anyway to prevent this?