Thank you so much! THAT is THE answer that I needed!
What I discovered now is that with the french culture (fr-FR), the point isn't allowed. But I checked the other culture available, and I found tha there is the swiss french culture (fr-CH) wich is the suitable language, and with it, the point work! It was all about that. Now, i don't understand why by default, the french french (if I can call it that way) is set. But anyway it doesn't matter! Thank you really much!