"A critical error has ..." installing Ubuntu under Win 8.1

[Warren Schubert]

Trying to create a new Ubuntu Desktop 12.04 guest on VBox 4.3.0 under Windows 8.1 Pro. During the Ubuntu setup get the following message from Guru Meditation:
"A critical error has occurred while running the virtual machine and the machine execution has been stopped."

I had also tried installing Ubuntu Desktop 13.10 in a VM. That time the install finished but got the same error immediately after the reboot and the installation end.

I do have 12.04 running fine under another Win 8.1 system, but that VM was created under Windows 7 before the upgrade.

Are there any settings I can try on my VM? Could I possibly copy the VM files from the other system over to the problem system and import them there?

[Warren Schubert]

I was able to Export Appliance and Import it on the problem system and it runs fine. This meets my most immediate needs though I'm still curious if I was doing something wrong in the set up.