Installing Mountain Lion 10.8 VM stuck on the kernel load

I am attempting to install a Mountain Lion VM on my Mac Pro (10.10). I am using VirtualBox 4.3.2. I was trying to follow these the instructions here, but I get stuck in the EFI boot sequence. I attached a screenshot of this.

I have tried the same process on my macbook pro laptop (with the same iso), and it works fine. I am not sure how to debug this, any tips or experiences would be greatly appreciated.