Problem with original Emacs LaTeX font lock scheme

I have set `TeX-install-font-lock' to the symbol `tex-font-setup', but
only strings and comments are fontified. Both `global-font-lock-mode'
and `font-lock-maximum-decoration' is `t'. Any clues?

Emacs  : GNU Emacs 21.3.1 (i386-redhat-linux-gnu, X toolkit, Xaw3d
scroll bars)
 of 2005-02-04 on bugs.build.redhat.com
Package: AUCTeX 11.55

current state:
==============
(setq
 window-system 'x
 LaTeX-version "2e"
 TeX-style-path '("style/" "auto/" "/usr/share/emacs/site-
lisp/auctex/style/"
                  "/usr/local/var/auctex/")
 TeX-auto-save nil
 TeX-parse-self nil
 TeX-master t
 )

-- 
August