So have you found Revit 2010 exports to Navisworks 2010 have some...well... little funny issues? Like not cutting walls where doors and/or windows exist? If so (or if you don't want to find out) you can get the HotFix Here.
What does ADSK say about the HotFix? They say that it..."Resolves issue with openings (e.g. windows and doors) being displayed as solid objects within Navisworks when using the Navisworks export plugin from within Revit."
Thanks to MM for cluing me in hours after this was made available!!!