Guest hangs on reboot

[Balanca]

Hi,

I have an old Windows 2003 32-bit server converted as a guest on Proxmox.

When I shutdown the guest (from inside Windows), everything is ok.
When I reboot the guest (from inside Windows), the shutdown starts and after 20 seconds I have a grey screen with the mouse cursor frozen and the guest never reboot.

If I copy/paste the kvm command line and run the guest from the command line (I just modify the vnc parameter) then I have the same problem.

/usr/bin/kvm -id 104 -chardev socket,id=qmp,path=/var/run/qemu-server/104.qmp,server,nowait -mon chardev=qmp,mode=control -vnc :100 -daemonize -smbios type=1,uuid=xxxxxxxxxxxxxxx -name xxxxxx -smp 4,sockets=1,cores=4,maxcpus=4 -nodefaults -boot menu=on,strict=on,reboot-timeout=1000 -vga cirrus -cpu kvm64,+lahf_lm,+sep,+kvm_pv_unhalt,+kvm_pv_eoi,enforce -m 4096 -k fr -device pci-bridge,id=pci.2,chassis_nr=2,bus=pci.0,addr=0x1f -device pci-bridge,id=pci.1,chassis_nr=1,bus=pci.0,addr=0x1e -device piix3-usb-uhci,id=uhci,bus=pci.0,addr=0x1.0x2 -device usb-tablet,id=tablet,bus=uhci.0,port=1 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 -drive file=/xxxxxxxxx.qcow2,if=none,id=drive-virtio0,cache=writeback,format=qcow2,aio=threads,detect-zeroes=on -device virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,bootindex=100 -drive if=none,id=drive-ide2,media=cdrom,aio=threads -device ide-cd,bus=ide.1,unit=0,drive=drive-ide2,id=ide2 -netdev type=tap,id=net0,ifname=tap104i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown,vhost=on -device virtio-net-pci,mac=3A:62:36:35:63:30,netdev=net0,bus=pci.0,addr=0x12,id=net0 -rtc driftfix=slew,base=localtime

I don't have the problem on another Windows 2003 32-bit guest.

I suspect something with ACPI, but I don't where to look at.