After updating Bios to version 0042 using the BIOS recovery process:
DIMM1 (Memory Channel A Slot 0): Not Installed
DIMM2 (Memory Channel B Slot 0): 8 GB
After swapping the 2 memory modules:
DIMM1 (Memory Channel A Slot 0): Not Installed
DIMM2 (Memory Channel B Slot 0): 8 GB
To me this seems that DIMM socket #1 is defective.
