Sounds like you built this system from scratch. One thing to check for is memory timings and voltage. It is very often the case that when you install new ram in a computer the motherboard does not correctly read it and will give it wrong default timings and, especially, wrong default voltage. Make sure you know what are the stock factory timings and voltage for your A-Data memory and then check the bios to see what it has assigned. Often ram has to be manually set in bios. Of course, if you are overclocking the memory bus then you need to bump the voltage up and perhaps relax the timings.