Copy VM from proxmox 1.3 to proxmox 2.2 : can't lock container XXX

Hello,

I'm trying to copy VMs from those two versions.
I'm using backup / restore.
It works fine for kvm vms but I cannot manage to do it for vz VMs :
# vzrestore vzdump-101.tgz 1006
can't lock container 1006

I tried using differents VMIDs, using -force true option, but still the same problem...

Any idea ?

Cheers.
Pascal.