No display with "new" ram

[Asusguy]

I've sent my 3 channel RAM for RMA because 1 stick was bad and so i've borrowed a corsair xms3 2gb stick from a friend, just for a few days. But the screen says no PC signal. I've tried resetting bios through battery removal, through jumpers, and through the reset cmos button. Still no luck.

I've also tried a mini boot, and i've tried changing sata cables and spots. still nothing.

System
i7 920
rampage 2 extreme
xfx 550 psu
gpu, tried with 4870 and 6950, same results

any ideas please?

 

[bamato]

Did you try re-seating the RAM? Are there any error beeps or memory lights indicating a problem on the motherboard? Did you mix brands of Ram on the same channel?

 

[Asusguy]

It looks like the RAM works on slot #5 only. Does triple channel memory have a culprit in which when a single ram is inserted, it can only work on slot 5?