9
To update your Newbb templates, go to System Admin - templates, Locate the newbb templates in your cloned template set, delete all of the existing templates then regenerate the templates.
One more question, make sure that you update the newbb module in System Admin - Modules. Also for rebuilding your default template set update the System module, same place.
What you have is fairly common with an upgrade, but there are several things that can cause it. But I still think in your case it is a template problem of some kind.
HTH.