PC shutting down when using Windows 7 guest on Linux host

[davoura]

I have a problem when running VirtualBox in Ubuntu Studio 16.04 with XFCE desktop.
It occurs sometimes when using a Windows 7 guest.
The PC will suddenly just power off for no apparent reason, it was not getting too hot as far as I can tell, and not much else was going on.
The PC has 4 GHz AMD CPU with 8 cores, 16 GB of RAM, plenty of hard disk space and Chrome and Thunderbird were running at the same time as VirtualBox in the host.
The shutdown can occur when just logging in to Windows 7 guest or after using it for a while.
VirtualBox is up to date, and this has occurred with previous versions as well.
I have tried using the same Windows VM in Linux Mint on the same PC in VirtualBox and it does not shut down the PC in Mint.
Is this a bug in VirtualBox or in Ubuntu Studio?

[socratis]

Is this a bug in VirtualBox or in Ubuntu Studio?

If anyone tells you that they know, based on the amount of information you gave, they would be lying. The information is not nearly enough to figure out what's going on. You need to provide the VBox.log (ZIPPED) of such a failed case.

When the VM aborts/crashes (that's what happens, right?), right-click on the VM in the VirtualBox Manager and select "Show Log". Save only the first "VBox.log", ZIP it and attach it to your response (see the "Upload attachment" tab below the reply form).