I have Ubuntu 14.04 64 bit installed in a virtual machine with 3 other OS's. GRUB is installed to the same partition as the ext4 (Linux) partition, rather than the MBR.
When I used Grub Customizer though, I think it may have written it additionally to the MBR. Not sure.
Anyways, some times when I boot the system and choose the OS from the boot menu (BCD boot menu) sometimes it loads fine and some time it gets stuck and I need to reboot it. Then it's fine again. See attachment to see the screen it gets stuck on.
When I used Grub Customizer though, I think it may have written it additionally to the MBR. Not sure.
Anyways, some times when I boot the system and choose the OS from the boot menu (BCD boot menu) sometimes it loads fine and some time it gets stuck and I need to reboot it. Then it's fine again. See attachment to see the screen it gets stuck on.