Won't POST with memory in dual channel

Hey there,

I have recently had a problem arise whereby my machine will not POST or display anything when I have memory in dual channel. My machine is a few months old and was working FINE with 4 sticks all in until yesterday.

I've got 2 Yellow followed by 2 Red slots.
If put 2 with different colours, its fine(no issues what so ever)
If I put 1 stick in double yellow or double red, it wont boot. Or if I put 3/4 in it has the same results.

Intel Core 2 Duo E8500 LGA775 'Wolfdale' 3.16GHz (1333FSB)
Sapphire ATI Radeon HD 4879 'Toxic' 512MB - x2(crossfire)
Gigabyte GA-EP45-DS3 Intel P45
Running Vista Home Prem 64Bit
Corsair TX 650W ATX


The only memory I have is Corsair 4GB DDR2 XMS2 PC2-8500C5
I have 6 sticks(had 2 from my old machine) and I have tried different combos of known working and the same issues occur regardless.

Example CPUZ memory page if any help - http://i33.tinypic.com/17v214.jpg

Any assistance would be appreciated

-Mattish