So I just got an extra 4GB of RAM in two 2GB matched pairs. I intend to get another 4gb for an even 8, but in the meantime 6 gb works. The problem is that DIMM 2 on both risers appears to be faulty (haven't bothered to try 3 and 4). The new RAM only shows up if installed in DIMM 1 on each riser, in place of the factory RAM. Additionally, factory RAM does nothing in DIMM 2. Are my riser boards faulty? MLB (I sure hope not)?