I'm using a Gigbyte 990FXA-UD3 with a 7970 & 5870 for Litecoin,Running about 900khs
You need to add a card,install vid driver,shut down,add a card,install vid driver,etc...
I'm with Easy on checking your bios settings.Or you may in fact have a defective board
BTW,I found GUIminer Alpha is WAY easier to use for Litecoin mining
https://litecointalk.org/index.php?topic=7722.0Use one instance per GPU & CPU
Here's for Nvidia:
http://www.litecoinminingmadeeasy.com/cudaminer-windows-guide.phpGood Luck!!!