New
#21
Does it matter which module? If not, I suspect it is a motherboard problem. There is also a small possibility that for some reason, the RAM modules themselves are incompatible with each other, but I assume it was bought as a kit, so that is highly unlikely. Which would be easiest to RMA, the RAM or the motherboard?
You could also see if you can get a pair from a friend and try it in your system dual channeled to rule out the RAM as the culprit.