Check the Crucial ram manufacturer's website for the latency and specially the voltage rating. The voltage rating should not exceed the specified voltage of your processor.
The settings from the XMP Profile in the BIOS for 1333 and 1600 match the Crucial specs perfectly.
I even reduced the latency to DDR-3 1066 to try and get the system to work.
Nothing helped.
Try increasing RAM voltage to 1.6 or even 1.65V. When all four DIMMs are populated, some motherboards do not supply enough stable voltage. I read this on Corsairs forums and it fixed my problems (I also have 8GB of memory and all slots populated).
Yes, try increasing voltage to 1.6 and then 1.65 if 1.6 does not work. It's NOT an issue of some motherboards not providing enough power, it's typically an issue of some RAM vendors requiring more voltage then they say they do. Perhaps even other board vendors "over voltage" by default. So if it's a voltage issue... it's not the board. But it's a good thing to try 
Using the XMP Profile in the BIOS sets the voltage to 1.65. All of the latencies match Crucial's Spec
Intel warns against raising the voltage above 1.6 volts in a flyer boxed with my motherboards.
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Can someone tell me what brand/model number of memory they are using that works in all four slots.
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Back to my original question, is it necessary to load the chipset drivers first, before populating all four slots.
Final Solution:
Crucial memory would not work with all 4 slots filled.
The Kingston Value RAM recommended from the Intel web site solved the problem
Crucial high performance Ballistic RAM would not work when all four slots were filled.
Kingston Value RAM listed in the tested memory section of the Intel site for the DP55KG board solved the problem.
I used OCZ Gold Series ram 4 gig per slot. First 2 slots work finr then I added 8 more gig to the last two slots of cucial CT2KIT51264BA1339 8GB PC10600 DDR3 1333MHz Dual Channel Desktop Memory Upgrade - 1333MHz, 2x4096MB, Non-ECC, Unbuffered total and wont boot. I have purchased another set of
that is recommended with the same results. All memory works fine first 2 slots. I am going to have to try the voltage increase as the list of recommend RAM does not include a 4 gig chip that could see. I will post the results later. This is very frustrating. The spec sheet on the mother board says do not go above 1.6 but all the chips say 1.65 . I am running a 750 watt power supply so there is plenty if current avalable. I have the 875K processor. My system is apart now but ran fine with vista ultimate 64 bit installed using the first 2 slots. THe recommend memory Kingston does not include 4 gig chips .
