We've been happily running Windows Server 2008 R2 in a KVM with ProxMox as a production file server for quite some time with few problems. Today we found the Win2008 KVM was no longer serving and when rebooted, it would go to a black screen after initially showing the Windows splash screen. It can boot to safe mode or recovery mode but nothing I can do lets it work with a normal boot. When we booted a 5-day-old snapshot of this VM on our backup host system, it was fine, but I see that it has significant Windows updates pending including a "Service Pack 1" that claims to have many enhanced virtualization features, and that requires a reboot mid-update. I'm wondering if anybody has observed the most recent Windows updates "breaking" a Windows 2008 KVM. I'll be experimenting with a copy of the backup snapshot (with an altered MAC address), hoping that Microsoft did not do something that will ruin what has been a nice, stable, flexible virtual hosting setup.