things are wrong here. Either you have a bad memory module or a bad memory slot. First try using all the modules (2 at a time) in the primary slots. If the system comes up and you have used all the modules then then one of the slots is bad. Doesn't matter which one, you won't be able to fix it. If it's still under warranty discuss it with ASUS support.

http://usa.asus.com/products.aspx?l1=3&l2=11&l3=244&l4=0&model=941&modelmenu=2

The url will bring you to ASUS's product page for your motherboard.

There's a slight chance you might be able to enable the secondary slots in the BIOS but I doubt it.

and life goes on...

Jack