mangOH VM not starting

I’ve downloaded the latest VM, and imported into VirtualBox.
When I start the VM, it just gets as far as ‘Booting SMP configuration’ - and hangs:

what does this mean? what should I do?

EDIT

On Win7-Pro 64-bit.

This is the ‘mangOH Dev using Legato 18.08.0 on Ubuntu 18.04 - r0’ VM
The other VMs start OK:
image

OK, found this: https://forums.virtualbox.org/viewtopic.php?f=6&t=84158

As suggested there, reduced the number of CPUs to 1 - and now it starts!
(disabling audio made no difference).

But one of the other VMs - which does work - has 2 CPUs:
image
So why should that one work with 2 CPUs, but this one fails with 2 CPUs?!

How will that impact on performance in my VM?