First, dig into the Source folders inside the AddressBook folder. Look in all the metadata folders. Make sure there are files in those folders. There should be one file for every contact, plus groups. They are named with unique identifiers, so you won't be able to tell what they are without quicklooking them.
If those files exist, find and delete every adressbook-v22.abcddb in each of the subfolders of Sources and the main AddressBook folder. Then, start Contacts and see if your contacts have returned.
If those files don't exist, or that didn't work, you need to recover the AddressBook folder from a Backup.
ho finnaly i found the solution !
Thanks to the TimeMachine, I reinstalled tho old version of contacts (from my last update, in august)
then i went to iCloud, cheked the box Contacts
and it's okay, it works, great !!! :-)
but it's the old version, so I hope it will still working after the update of Lion Mointain 10.8.2 !