I'm not certain about this but just as my DG45ID doesn't allow booting from over 2 TB RAID Volumes (even with UEFI enabled in the BIOS), I suspect this is down to Intel not really offering TRUE UEFI support (with everything associated such as very large volume support). Maybe someone at Intel can confirm this but I suspect you're going to be stuck with having to turn off UEFI. You should try updating the boards BIOS to the latest revision to see if that makes a difference (it didn't with my DG45ID because that's *apparently* a hardware limitation).
Edit: Just saw you mentioned the board is already up to date (so I assume that means the latest BIOS). I guess your only option now would be to contact Intel tech support and see what they have to say about it. Keep us informed!