Activating EFI boot (Settings->System->Motherboard) in my Virtual Machine appears to have fixed the issue for me as well (Windows 10, 64 bit, VirtualBox 5.1.2)
Activating EFI boot (Settings- >System- >Motherboard) in my Virtual Machine appears to have fixed the issue for me as well (Windows 10, 64 bit, VirtualBox 5.1.2)