GA-MA785GM won't post with 2GBPK and 2GBHK

[nosoup4u]

Motherboard: Gigabyte GA-MA785GM-US2H
CPU: AMD Athlon 64 X2 Dual Core 2400MHz
RAM: F2-6400CL4D-2GBPK and F2-6400CL4D-2GBHK

The system will post/run/test fine with either pair of memory but not both. When both are present the CPU fan seems to slow down during post and the system freezes. Per a message on the forums I set the memory setting to the PK timings (slower) for both sets. I also increased the RAM, CPU and NB voltages. Nothing helped.

Is it possible that one these is drawing too much power? What next?

[Tradesman]

Big differences in timings and slight in voltages, could try maybe 4-4-4-9 at 667 speed, w/ 2 Volts and Command rate at 2N, will also want to check tRFC prob around 160....................but, I wouldn't bet on it...what does AUTO set them at with PKs in the lead slots