Problem of unable to login (flashing curosr at top left of screen) after installing Debian Mint (64 bit), completing the updates and then installing the Nvidia drivers etc from Synaptic.

Use the information from http://verahill.blogspot.com/2012/01/debian-testing-64-nvidia-gt520-issues.html
 which solved the problem (see the the first comment/reply at the bottom of the page), but slightly varied.

1- After fresh install of Debian Mint (64 bit) 
2- Install updates
3- Open a terminal and run the following:
    sudo apt-get install nvidia-kernel-dkms nvidia-settings nvidia-smi   nvidia-xconfig
 4- Next: sudo rm /etc/X11/xorg.conf
 5- Next: sudo rmmod nouveau
 6- Next: sudo nvidia-xconfig
 7- Next: sudo gedit /etc/modprobe.d/blacklist.conf

Add a line at the bottom that says: blacklist nouveau

 8- Save the file
 9- Shut down and reboot, everything should  be fine and Nvidia X Server Settings should be present in:

System/Administration