Thanks for your answer. No I want to export in a new folder on desktop, that I named "family" NOW I just try to change the folder name and surprise it works !!! I dont have any folder on my desktop named "family" i cannot understend, but the important thing is that it works. I wish you a great day from Switzerland.
I found the problem. On the desktop I have a shortcut for an external harddisk called "family". Of course LR can't create a new forlder with named "family" and can't save the photo in this folder. Thanks for your Help.