So I have a HP Proliant ML10 v2 and 3x4Gb G Skill Ripsaw X DDR3-1600 PC3-12800 1.5V. The computer does not show POST and then proceeds to a long beep. I removed the new RAM and boot and then everything is OK again.
Here is the RAM: http://www.newegg.com/Product/Product.aspx?Item=N82E16820231428. I'm sure that it is unbuffed DIMM.
I think it might be a problem with: 1. Defective RAM (unlikely but might happen) 2. BIOS