Same question from me!  I would really appreciate  knowing this one.
		
	 
	
	
	
 
		
			
	
	
		
		I was able to get this partially accomplished using the Members Only plug in. Also, it helped a lot to put all my forums in a category, even though I do not have very many forums. At least, now the only thing my non-users will see is the goofy message “Oh brother.  No forums where found here”, even though I do indeed have forums.  
HOWEVER, I still have the problem of the Forum Menu item appearing in my menu bar.  I don’t know how to keep it out until users log in.  
I’ve spent the better part of a day fiddling with it and still it is here. 
If I can figure out which file has the “Oh Brother!” text in it, I could at least change it to say something like “This area requires user authorization”.