Project with several directories added now silently refuses to add a particular directory

[Karr, David]

I've been using Source Navigator for a few days now, and I find it works
pretty well.  I've added several directories from a large project, and I'm
able to view and navigate those files well.  I'm now trying to add another
directory, which is a "peer" directory of one of the directories I've
already added.  When I press OK on the "Add Directory" dialog, the project
directory tree refreshes, and that new directory is not displayed.  No
matter what I do, I can't get this directory into my project.  I don't get
any error messages, it just silently refuses to add the directory.  I'm
using version 5.0.0 on Win2k.