Check your Database Folder and Backup Folder file paths.
There is a known bug where FMS 10 that might explain this. FMS 10 will accept a path as "valid" on the console screen when it is not in fact valid due to a missing slash. If I remember correctly, this happens if you leave out the slash either before or after the drive letter.
Thanks for your answers. It helped me to find the cause of the trouble.
What was true is that the Filemaker Server console returns me that a path was valid when it wasn't.
The problem what not one of a missing slash. It dealed with the alternative default folder for data.
According to white papers, I've divided the hard disk of my server in 3 volumes "C:" for the system, "E:" for the data "F:" for the back-ups.
And in the preferences of the Filemaker admin console, I've simply specified "filewin:/E:/" as alternate folder for the data.
The folder "birdy-serveur-principal"of my solution is placed at the root of the volume "E:"
The problem was solved by specifying ""filewin:/E:/birdy-serveur-principal/" as alternate folder for the data.
Thanks a lot for the inspiration