virtualbox.org

I have VirtualBox 4.2.6 on Win7 x64. My system is a Sony Vaio Z, with an Intel i5 CPU. Sony updates does not retrieve any updates for BIOS or such.

I have created a standard Ubuntu guest with the wizard and attached a premade Turnkey Rails 11.3-lucid-x86 vmdk disk.

When the guest shuts down, the Windows host goes blank and restarts.

This happens both powering off the guest and using the graceful guest shutdown sequence.
I have tried with different guests: Ubuntu, Win7 x64. I also tried to change chipset from the default PIIX3 to ICH9, always the same.
My system has a double video card. The less powerful video card takes over the main one when I switch on battery. Anyway all the tests where made having the power cord attached.

The log is attached.

Thanks for help

Find where to turn this on in your bios and see if that helps.

You were right, virtualisation extensions were disabled.
I enabled virtualisation extensions in BIOS, but VB still crashes the host.
Anyway I checked VMware player can go both with and without extensions. So it should be something else.

I attached the log of a new test with m0n0wall (Freebsd).