I could maybe try updating the bios, supposedly the latest one has better memory support.
^for (b): if this board is new and within warranty period i would be going back to the etailer for an RMA pronto
if it is indeed a bad BIOS ROM then flashing a new BIOS into a dodgy ROM might be the straw that breaks the camel's back, and wreck the whole board. if this happens then the RMA is likely to be rejected as they could argue user error
you bought a prebuilt with a warranty. i would highly suggest you use said warranty.

