Hi,
As mentioned, I had already attempted a BIOS recovery using the Jumper - and that should imply the of the MK0065.BIO file on a USB Flash-Drive - but that failed. Power-on now sees the CPU fan spin up, but nothing else happens, and nothing displays on the monitor.
The board is certainly quite useless now, but there was absolutely nothing wrong with it prior to attempting the v65 upgrade, and then attempting a BIOS recovery after the former failed.
The 2nd board that also failed to apply the v65 update (and then issued numerous error messages before finally booting) was a new, and previously unused, one.
I'm concerned that this 2nd board may now be in an unstable condition, but I'm extremely reluctant to attempt a BIOS recovery, lest I end up with no working boards at all.
I struggle to see how this can be considered to be a 'defective' motherboard issue, and feel that this is far more likely to be an issue with the standard BIOS updater - MKQ7710H.86A.0065.EB.EXE.
I'm no newcomer to this, and have been working with Intel boards (both desktop and server) for many years, and this is the first time I've encountered such an issue.