Debian amd64 (wheezy): gnome 3 not working

Debian amd64 (wheezy): gnome 3 not working

I can not start gnome 3 on my laptop. I have got a popup message that problem may be in graphic drivers. I used this instructions http://wiki.debian.org/NvidiaGraphicsDrivers#Version_304.88 but no success. My video-card is
nvidia geforce gt 520mx
I also created file
/etc/X11/xorg.conf.d/20-nvidia.conf

Section "Device"
    Identifier     "My GPU"
    Driver         "nvidia"
EndSection   
Also I used command:
nvidia-xconfig
But every time I got a black screen (after rebooting) with blinking cursor.
To start gnome 2 I just delete file
/etc/X11/xorg.conf.d/20-nvidia.conf
Or that file which was created after command:
nvidia-xconfig
what I am doing wrong? How to fix this (I mean how to start gnome 3)?