1. Find a System category with at least two classes with a single 
method category of the same name, typically: 'as yet unclassified'.

2. Open a System Browser.  Select the category and one of the 
classes.  Select 'as yet unclassified'.

3. Select the other class.  'as yet unclassified' remains hilighted, 
even though no methods are shown.  (VERY disconcerting if you have 
been working on that class for some time and fear having lost all 
your work.)  All is well though: as soon as you click on 'as yet 
unclassified,' your methods are properly displayed.