In NetBeans 6.7rc1 on my Mac OS X 10.5.6 MacBook, choosing Tools > Libraries displays the "Library Manager". (By the way, notice that menu item's label 
does not match the documented feature name and the window's title).

In the Library Manager, I click the "New Library" button. A dialog asks for a name. When I type a name with a space, a red colored label says "The library name 
contains invalid characters". Strange, but fair enough. But then I noticed that half the items in the existing default list of libraries have spaces in their names, 
such as "Absolute Layout", "Beans Binding", etc.

--Basil Bourque