I've been getting messages popping up in the guest telling me my battery was low even though the laptop was running on AC. Also when running a guest I would have occasional problems with my screen blanking and not being able to get it to come back to life. When searching the web for information about the latter I ran across ACPI posts. I've disabled ACPI on my guest machines (using these steps) and my problems seem to have gone away. Turning off ACPI doesn't seem to impact performance or operation on my guests.
Does anyone know if VirtualBox wants or needs ACPI to be enabled on a guest?
Thanks -- Robert