Tracking down errors in validation

Hi all.  I have recently tried mlview for learning XML and DTD's, and
have not yet figured out how the mlview displays debugging errors for
invalid documents.  I have an inline DTD in my XML doc; when I click
Action -> Validate Document, I get a popup saying that the document is
not valid, but no other information is given.  Does mlview give any
error information such as which line has returned an error?  

Also, because this document is not valid, mlview seems to have a problem
displaying the tree.  It tries to display the DTD Node within the tree,
but the text changes and flutters strangely, ultimately displaying empty
space.  Here is the Gtk error messege that I get in console:

 (mlv:19974): Gtk-WARNING **: Failed to set cell text from markup due to
error parsing markup: Error on line 1 char 66: Element 'markup' was
closed, but the currently open element is 'span'

Also, please reply to my email address above as I am not (yet)
subscribed to this list.

Thank you in advance,
Dan