Hi,
It sounds like there is a problem with the driver, try uninstalling it and then reinstalling. If that will not work uninstall it again and reboot windows and let it reinstall the driver. If you still have problems, download the drivers from the net and then reinstall.
Is there any yellow or red marks with the listing of your monitor in "device manager" ?
What were you running before?
Have you tried to use the old monitor with the new card?

Hi again,
Also try to run the monitor off the main board with no card, you will have to remove the card for the on-board card to work.