Proxmox 3 Snapshot VM

Hi,
i'm sorry for my english.

i have installed a new ovh server with proxmox 3 (default installation).
Promox work good but i can't create snapshot because the menu "Take Snapshot" is disabled.

My VM is a debian iso in local storage (default storage) and QEMU image format (qcow2).

Can you help me??

Thanks!

Best regards