BTW, with most modern computers any USB storage device should show up in the Boot list, (when you press F11 or F12 usually at boot instead of Del), does it ?
nope, doesn't show up in bios (it's a uefi board, if that makes any difference)
If there was a hardware issue with the mobo I'd expect to have trouble with the USB ports consistently, not just with a particular device
Does the machine react (installing USB device) to the drive being plugged in at all? I've seen several storage devices try to grab the same drive letter as a mapped drive, which causes both to try and show up under the same letter. If that's the case the disk management console will let you force it to an accessible drive letter.
been caught by this one before, but nope, it's not detected, at all
That said, the lite on the drive flickers, so there is
It's generally not recommended you plug an external HD into a hub.
I did this after trying all the motherboard ports - a bit desperate, but there's no logic here so...
I use 'high powered' hubs (external 2A PS) so power shouldn't
be an issue, but who knows
Something easy to try, plug the drive into a USB 2.0 port on the suspect computer and boot off of a Linux LiveCD - it will at least isolate it to software or hardware.
Tried Mint x32 and it didn't recognise the drive at all (I'm not a linux user so maybe there's something 'special' I needed to do)
I'm wondering if this isn't some sort of firmware issue in the HDD, though there doesn't seem to be an update available, and as I said, the issue doesn't appear to be specific to any make or model of drive.