I had the same problem as you, normaly this is caused by a problem with X.org reading the EDID file from your monitor with the resolutions...
The solution is to edit the
/etc/X11/xorg.conf file like this :
If you don't have this file then you have to create it from scratch, just let the Nvidia software do it for you using this command on the terminal :
If you already have an
xorg.conf file, then you'll just have to edit (or create one if he doesn't exist), as root, like this:
gksu gedit /etc/X11/xorg.conf
And copy this lines on the "Section Device":
Option "UseEDID" "true"
Option "IgnoreEDIDChecksum" "CRT,DFP,TV"
If you are using and HDMI cable (for example), and the image is not scaled then add this line just after the other ones:
Option "FlatPanelProperties" "Scaling = Native"
Now just logout and login again, Open the "Nvidia X Server Settings" and see if all the resolutions available by your display are available.
I hope this helps.