Changing window managers (Gnome 2.4)

[Soumyadip Modak <soumyadip@softhome.net>]

I've Sawfish running as the window manager for Gnome 2.4. I intend to
use Metacity. I installed Metacity (i'm running Debian, so i apt-get
install-ed it), but now i can't find a way to make Gnome use Metacity
instead of Sawfish. Googling around posted 2 possible solutions :

1> Use metacity --replace
2> Use killall sawfish; metacity

When i run either of the 2 alternatives, i get :

modak:/home/soumyadip# metacity --replace
Window manager warning: Failed to a open connection to a session
manager, so window positions will not be saved: Authentication Rejected,
reason : None of the authentication protocols specified are supported
and host-based authentication failed
Window manager warning: Screen 0 on display ":0.0" already has a window
manager

modak:/home/soumyadip# killall sawfish; metacity
Window manager warning: Failed to a open connection to a session
manager, so win dow positions will not be saved: Authentication
Rejected, reason : None of the a uthentication protocols specified are
supported and host-based authentication fa iled
Window manager warning: Screen 0 on display ":0.0" already has a window
manager

I've already run update-alternatives --config x-window-manager. It shows
:

modak:/home/soumyadip# update-alternatives --config x-window-manager
 
There are 3 alternatives which provide `x-window-manager'.
 
  Selection    Alternative
-----------------------------------------------
      1        /usr/X11R6/bin/twm
*     2        /usr/bin/metacity
 +    3        /usr/bin/sawfish
 
Enter to keep the default[*], or type selection number:

Metacity has been selected as the Default window manager, but somehow
sawfish is starting up. I'm stumped! Can anybody point me out to any
resources i can refer to to correct this problem ? 

Thanks a lot
-- 
Soumyadip Modak <soumyadip@softhome.net>