I had the same problem my first install.
Had to reinstall it again.
Then I figured out where to look to fix it.
http://www.redhat.com/docs/manuals/e...iguration.html
Look in the /etc/X11 directory and look for xorg.conf.
Here you can edit the Monitor section and write in the values for your monitor. Be careful though and make sure you use the real values for the monitor.
I'm still a Linux noob....so that may not be everything.....good luck.