Thanks for your answer. I'm waiting for a backup of my database and i'll try to uninstall it / reinstall it.
http://www.sheeloo.net/div/polylang.jpg
As you can see here, I've found something in the DB, it's a good thing.
But it seem to be a DB Polylang 1.1.6 isn't it ? Or, i have the 1.2.3...