Hi,
I have the same problem as above, Windows 2012 won't install but 2008R2 does.
Also tried the CPU trick which helps with installing 2012 but on first boot an error "the computer encountered an error and wants to reboot" and stays in this loop.
Putting the CPU back to the default does not help with this issue.
Strangely the computer installed and ran Windows 2012 perfectly just a few months ago.
In that time the computer had a apt-get update/upgrade and was there a update for JAVA.
At first i was thinking it was a bad ISO image but i tested them with Virtualbox and the images are perfectly working.
I also installed Proxmox again on the systems ( running proxmox on 3 test servers, all have troubles with Windows 2012 now.
the only concussion i can get at is some update is screwing up proxmox from working with Windows 2012.
pveversion -v :
proxmox-ve-2.6.32: 3.1-109 (running kernel: 2.6.32-23-pve)
pve-manager: 3.1-3 (running version: 3.1-3/dc0e9b0e)
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: 4.0.0-1
pve-cluster: 3.0-7
qemu-server: 3.1-1
pve-firmware: 1.0-23
libpve-common-perl: 3.0-6
libpve-access-control: 3.0-6
libpve-storage-perl: 3.0-10
pve-libspice-server1: 0.12.4-1
vncterm: 1.1-4
vzctl: 4.0-1pve3
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 1.4-17
ksm-control-daemon: 1.1-1
glusterfs-client: 3.4.0-2
qm config:
bootdisk: sata0
cores: 1
cpu: host
ide2: local:iso/Windows_2012R2_X64_Essentials.ISO,media=cdrom
memory: 4096
name: addc
net0: e1000=8E:FC
E:49:AF:B5,bridge=vmbr0
ostype: win8
sata0: local:100/vm-100-disk-1.qcow2,format=qcow2,size=50G
sockets: 1
** the config for the virtual machine has been used for both Windows 2008 and Windows 2012 servers in the past. **