G.Skill on an ASUS

Hi,
I just got a new desktop and wanted to install 32 gb on it but it wont accept:
Sabertooth z77 MB
G.Skill RipJaws ddr3-1600 - 32gb (4x 8gb)
intel i5-3570 ivy bridge 3.4 GHz
Running windows 7 ulti 64bit

I dont think the other components matter

But my problem is that I can install on the a1 a2 slots my memory up to 16 gb. when I try to add anything to the b1 b2 slots for memory, the red memOK light shows up and my computer wont run. screen stays black.
I went into bios and changed my memory speed to be at dd3-1600, and sitll no good. It just won't accept anything in my b1b2 slots. What would i need to do to fix that?