when you edit your forums in the controlpanel and setup subforums ist shiould look like this:



If your Browser windows go to small this happen:



It doesn't show sroll bars and breaks the layout. The first time I see it I dont remind thats only the windows of my browser is to small and I start to searching what goes wrong with my subforums bevor I note its only my browser window.

Added in a nowrap on the table cell that holds the forum name. That will fix it for b2.