Hello Andrea, thanks for your very useful reply and for the links.

2014-06-28 16:29 GMT+02:00 Andrea Rossetti <andrea.rossetti@gmail.com>:
I had the same problem some time ago. That variable
has been removed in recent Org versions, and you
probably have (like me) an old built-in Org "shadowed"
by a new Elpa Org. You should ignore that variable.

How can I remove this old built-in Org "shadowed"
by my new Elpa Org ? It seems to me that it should be the best solution, but I do not want to broke my org installation because it works well, this detail excepted.
 

Thanks again for theses links.

Best regards,

Jo.