Phantom Error in Deployment Descriptor

This one has lost me many hours.  Every once in a while I'll do something
(what, I'm not sure) that will create a "phantom error" in a web project.
In Project Navigator, the project will have an error indicator.  When I
expand the project, the only thing that shows an error is the Deployment
Descriptor.  When I expand the Deployment Descriptor, EVERYTHING in the DD
has an error (Servlets, Servlet Mapping, Filters, et al).  However, I can't
find what the error is, so I can't change it!

When I double-click on the deployment descriptor, I get the Web Deployment
Descriptor editor.  It starts out on the Overview tab, which is completely
blank.  I then go through each tab and see no errors.

The Overview tab being blank is a bit strange, but it's that way on every
web project, errors or not.  It's been that way for so long that I forgot
about it, and maybe that's related to my problem.  But I have created many
web applications that work just fine, yet have blank Overview tabs.  As a
test, I just created a completely new workspace, created a Web Application,
and the Overview tab was blank.

Any of this ringing any bells with anyone?  And are your Overview tabs blank
like mine?

Joe