I can confirm that I am experiencing the same problems:
Using schema /usr/share/emacs/site-lisp/nxml-mode/schema/xslt.rnc nxml-maybe-load-char-name-set: Internal nXML mode error in nxml-fontify (Cannot open load file: /usr/share/emacs21/site-lisp/nxml-mode/char-name/unicode/1D400-1D7FF), degrading
