Go to Manage > Categories.
If you're on 0.6.x, you need to edit each category and add each moderator one by one by typing their username, then clicking their permissions, and selecting Moderate.
If you're on 0.7.x dev build, you can click edit on the category, and set Moderate on your Moderators group.
LOL can you repro?
Nope. Only happened once. tbh I nearly refreshed when it did it without print screening it. Might only do it when you have 1 post in the topic.
It could also be my new fancy internets being too quick and showing me two topics at once like some mental multi tasking feature.