Rendering Problem in Firefox or Netscape

We have XML pages which are not rendering with Firefox or Netscape but work
fine with IE6.  Another branch on the east coast also has the same schema
based pages and we have no problem seeing theirs.  I have compared the MIME
type, encoding, namespaces and all are the same, yet our pages have
problems.  I have posted a very stripped down sample page and stylesheets on
my homesite for your assistance. 

http://www.kenandtiffany.com/XML/niprnet_test.xml

The only difference between their pages and ours, other than the data in the
XML fields, is their stylesheets are 2 deep where ours are 3 deep.  However,
in testing this, this doesn't seem to matter as the posted example is 2 deep
as well. 

Please take a look and if you can help us it would be greatly appreciated.

Ken Roberts