problem with first x session after installation

[Frederico Rodrigues Abraham]

Hi.
I have just installed debian sarge from the first dvd and was surprised that logging in with my normal users doesn't work (i've had no problems with it using the same dvd)

When i log in, i am automatically logged out.
My .xsession-errors says:
-----------------------------------
/etc/gdm/PreSession/Default: Registering your session with wtmp and utmp
/etc/gdm/PreSession/Default: running: /usr/X11R6/bin/sessreg -a -w /var/log/wtmp -u /var/run/utmp -x "/var/lib/gdm/:0.Xservers" -h "" -l ":0" "ugah"
/etc/gdm/Xsession: Beginning session setup...
Xlib: connection to ":0.0" refused by server
Xlib: Protocol not supported by server

xrdb: Can't open display ':0'
Xlib: connection to ":0.0" refused by server
Xlib: Protocol not supported by server

xrdb: Can't open display ':0'
Xlib: connection to ":0.0" refused by server
Xlib: Protocol not supported by server

(gnome-session:7461): Gtk-WARNING **: cannot open display:
-----------------------------------

What is wrong ? I didn't do anything different from before... using 'linux26' to install debian, selecting 'desktop environment' in tasksel, and after the installation, trying to log in.
Detail: i had to install the nvidia driver because the 'vesa' driver didn't show anything. I have done it using the steps described in http://people.debian.org/~rdonald/index.php

Thanks
    -- Fred