Crossfire not working anymore.

Hi guys.
I flashed my bios with the last one available because the clear cmos switch jumper was not working.
After flashing the bios the system does not detect the second graphics card.
I tried using the cards one at a time, they both work.
the specs are:

mobo: asus sabertooth p67
2x4 gskill ram
core i5 2500k
2x msi hd 6950
chieftec 88+nitro 750w
corsair force 3 120gb ssd

Thanks