Gtk can't find themes

["Marcus Habermehl (BMH1980)" <bmh1980de yahoo de>]

Hi.

I've installed Gtk+ 2.10.6 on Linux LFS in /opt/gnome.

My Gtk+ themes are installed in /opt/gnome/share/themes, 
/opt/xfce/share/themes and /usr/share/themes.

That's because I'm installing packages by the domain names.

If I want to use an other theme, I can only choose themes from 
/opt/gnome/share/themes. All others are ignored.

Why can't Gtk+ find the other themes or theme engines?

I've set:

GTK_PATH=/usr/lib/gtk-2.0:/opt/gnome/lib/gtk-2.0:/opt/xfce/lib/gtk-2.0
XDG_DATA_DIRS=/usr/share:/opt/xfce/share:/opt/gnome/share

As I'm understanding 
http://developer.gnome.org/doc/API/2.0/gtk/gtk-running.html that's 
correct. Or I'm wrong?

Greetings
Marcus