Hello
When I try to save gallery options, it is automatically reset to blank for most of the fields... furthermore, the site is not displayed in the same way if I put www.flahautshop.com or flahautshop.com... an idea ?
Thanks and regards
Xavier

Please review your Zenphoto debug log and also the server php error log (ask your host where to find that if you don't know).

The site looks the same for me under both urls. In general your server must be properly configured to support the url version with www subdomain and without. Ask your host about that.