Latest BIOS *is* 650, available here: Download BIOS Update [SIX7910J.86A].
What I meant was, have you checked in the runtime environment to see whether VT-d is automatically being enabled when you enable VT? They may have decided to just not support this as being enabled separately.
I didn't. But I'm pretty sure I identified the issue based on my research.
My CPU is the E5-2670v1 SROH8 (C1 stepping). From the info I found, there was a bug with VT-d on that CPU that made it unusable. That was only fixed on the SR0KX version (C2 stepping).
Issue is with the CPU not the motherboard or BIOS.
Thanks for your help Scott!