What's the max voltage your RAM can take according to spec? make sure you're not undervolting or overvolting your RAM.
Mem timings apart from the ones you set can be left on Auto.
if 4-4-4-12 doesn't post, try 5-5-5-15 and then Memtest, if that post's ok try 5-5-5-12.
You might be better off enabling Transaction Booster and setting it to 0, also set Ai ClockTwister to Strong.
If you find that this works, try putting Transaction Booster on 1 afterwards.
Some people say that Transaction Booster doesn't work properly, but it works fine for me and increased my mem read speeds a little.
If increasing the latency helps you to post, you can probably try to drop the North Bridge volts a little, but that's only worth doing if you are worried about temps! if your NB is staying below 58-60c then you should be fine.
Refer to
my post earlier regarding my listed BIOS settings if you are puzzled with setting up voltages.
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