XPS 720 H2C won't post with (4) 2GB modules

Following is my post to the OCZ forums, I am using the new Reaper HPC 2GB PC2-8500 modules.  The system runs great with 2 of them, won't post with all 4 mounted.  The system boots and runs fine with the factory shipped Nanya (4) 1GB modules.  I've tried CMOS reset, I've tried disabling SLI/EPP prior to inserting the 3rd and 4th module.  Not much else I can do if the system won't boot.

• OCZ part number:-OCZ2RPR10664GK
• Module size and kit size:-2 x 2gb kit (x2)
• CPU model and rated speed:-QX6700, 2.66ghz
• Overclocked CPU speed:-3.2ghz
• Divider and FSB used:-1066mhz
• Motherboard and revision:-Dell 680i
• Motherboard Bios rev:-A05
• Video card:-nVidia 8800GT x2
• Power supply:-Dell 1100W
• Operating System:-Vista Ultimate x64
• CPU and System Cooling:-Water and good airflow
• CPU and System temps:-cool
• Purchased at/on:-ZipZoomFly last week
• Country:-USA
• Memory voltage:-2.10

Having problems with all 4 modules installed. 2 modules work fine and at the rated speed. With 4 modules installed the system will not post. This is a Dell XPS 720 H2C system. I have limited BIOS tweaking options. For memory, I have the choice of SLI/EPP for memory or not. I've tried CMOS reset, SLI/EPP disabled and am looking for other suggestions. Little I can do if the system will not post.