There are a few possibilities to consider on this one - firstly the processor is not "officially" compatible with the motherboard, secondly the memory is not "tested" as compatible with the motherboard, and thirdly the power supply does not sound like an ATX 2.2 compliant PSU which is recommended. There is a tested list of memory for the D975XBX2 here -
and a list of supported processors here -
Maybe try using components from these lists as 8GB is the max on this board and it may be quite sensitive as to the memory used. Additionally, it may depend on the graphics card that you are using as the graphics memory will require an equal amount of physical memory to be allocated to it. If running a board with the maximum amount of memory (8GB), it seems that tested/compatible components work best!