If you haven't already done so upgrade the nvidia drivers. Download from website, hit ctrl alt f2, go to the directory where you download the drivers. type telinit 1, that will kill x. then sh N Tab that should bring up the command you need to install the driver. Why am i telling you all this here's a link.http://forum.linuxmce.org/index.php?topic=5398.msg31667#msg31667
If that doesn't help post back, by the way which dvd did you install. If it wasn't the i386 version you might want to give that a try. I have a xfx 8500gt and the i386 version worked right off the bat. Just had to upgrade drivers to get the dvi to hdmi to work.