Cannot install 8Gb RAM on GA-P35C-DS3R

[Dela]

Hi,
I'm having problems installing 4x 2gb of RAM on my gigabyte motherboard GA-P35C-DS3R. I bought 2x Corsair CM2X2gb 800MHz (5-5-5-12) and they worked perfectly. I bought another identical pair and the computer won't boot, no bias or even a blue screen, it's just black. I later found out that they had latency of 5-5-5-18 even though they should have been the same as the existing one. I don't know if this is causing the problem. The new RAM works fine on its own just not when I mix it with the existing ones. I tried every combination on the motherboard slots and they all work fine. I've even tried upping the RAM voltages but still nothing. Any ideas or similar problems? Any help will be appreciated. Thanks.

My Specs:

Q6600 (Not overclocked) 2.4GHz
GA-P35C-DS3R motherboard
4 x CM2X2048-6400C5 (2x 5-5-5-12 and 2x 5-5-5-18)
7800GT
Vista Home Premium 64-bit

 

[WazzaUK]

Yep.... all installed DIMMS should be the same specs (dual channel)...

 

[Dela]

Ah okay. Is that why I can install 6Gb if two are matched and one is on its own? If there's no work around I'm gonna send them back to the supplier. They were all meant to be 5-5-5-12 anyway.