I updated my Proxmox system two days ago to the current pve-no-subscription packages. The update finished without any error messages and I restarted the Proxmox server. Right now the following software versions are installed on the server:
Everything went fine for one and a half day but then the KVM-VM with Windows Small Business Server 2008 had a blue screen with the error message IRQL_NOT_LESS_OR_EQUAL

I experienced the same problem some months ago. I solved this by selecting the CPU type "host" instead of "Default (kvm64)".
Does somebody have a hint how I can fix this problem or at least get a more detailed report about the reason of this BSOD. Because I can't find any hint for the reason of the BSOD in the logs of the Windows VM or in the logs of the Proxmox server.
Code:
# pveversion -v
proxmox-ve-2.6.32: 3.2-126 (running kernel: 2.6.32-29-pve)
pve-manager: 3.2-4 (running version: 3.2-4/e24a91c1)
pve-kernel-2.6.32-20-pve: 2.6.32-100
pve-kernel-2.6.32-28-pve: 2.6.32-124
pve-kernel-2.6.32-25-pve: 2.6.32-113
pve-kernel-2.6.32-29-pve: 2.6.32-126
pve-kernel-2.6.32-26-pve: 2.6.32-114
pve-kernel-2.6.32-23-pve: 2.6.32-109
lvm2: 2.02.98-pve4
clvm: 2.02.98-pve4
corosync-pve: 1.4.5-1
openais-pve: 1.1.4-3
libqb0: 0.11.1-2
redhat-cluster-pve: 3.2.0-2
resource-agents-pve: 3.9.2-4
fence-agents-pve: 4.0.5-1
pve-cluster: 3.0-12
qemu-server: 3.1-16
pve-firmware: 1.1-3
libpve-common-perl: 3.0-18
libpve-access-control: 3.0-11
libpve-storage-perl: 3.0-19
pve-libspice-server1: 0.12.4-3
vncterm: 1.1-6
vzctl: 4.0-1pve5
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 1.7-8
ksm-control-daemon: 1.1-1
glusterfs-client: 3.4.2-1
Everything went fine for one and a half day but then the KVM-VM with Windows Small Business Server 2008 had a blue screen with the error message IRQL_NOT_LESS_OR_EQUAL

I experienced the same problem some months ago. I solved this by selecting the CPU type "host" instead of "Default (kvm64)".
Does somebody have a hint how I can fix this problem or at least get a more detailed report about the reason of this BSOD. Because I can't find any hint for the reason of the BSOD in the logs of the Windows VM or in the logs of the Proxmox server.