The memory was set to 32MB, I changed it to 512MB just for the fun of it but it made no difference. I have 8GB of RAM in the NUC.
I actually have the 2.5" model of the NUC, so I am not currently using the mSATA port. Instead my main harddrive is a 2.5" Samsung EVO 840 250GB.
I also tried just now to add a delay in the BIOS when it engages the HDD, it was set to 0 seconds. I changed that to 5 seconds, now the INTEL NUC is actually displayed on both screens at startup but from there on out it does not progress further in the boot process. Super annoying right now.
I will have a look at the link you sent me, thanks.