It sounds like X is not configured correctly. Before doing the following press CTRL+ALT+F7 to see if a graphics screen will come up.
If that does not work, try is booting into recovery mode and running dpkg-reconfigure xserver-xorg. For most of the answers, take the default.
For items like screen resolution, give yourself a few choices, so you can experiment when you get the x driver running.
If you're using a proprietary driver, consider using vesa.
Of course, before doing any of this, it would not hurt to log into the X-term login, and go explore the logs under /var/log to see if you can find out why X won't come up.