One of my server 2008 R2 virtual machines keeps turning it self off after a while. I'll leave it running for a while and find it not running any more. I need this running until I decide to shut it down. I have another server 2008 R2 system that doesn't shut it self down.
How do I keep this system / virtual machine running 24/7?
Which VB version and which Guest Additions version? There was a small issue with 4.0 and I believe 4.0.2 as well, that some ACPI options were available to the Guest OS that made it possible to suspend and even hibernate after a given amount of time. So check the power settings or at least update VB and the GA to the current release, 4.0.8.