Hi Jayden,
The memory inserted is exactly the same and is also correctly recognised by the BIOS of the machine.
Originally the machine was having 4 * 8 GB. After inserting an additional 4 * 8 GB the boot fails.
Furthermore, as a test, I have removed all the memory and replaced it in the original banks with exactly the same DIMMS of 4 * 16 and the same problem occurs.
So it seems that whatever combo I put over 32 Gb (either 8*8 or 4*16), the OS fails half fail during the boot cycle..