Hello lechatbleu,
Apologies if I did not quite follow, as I had to use Google Translate.
I would suggest you try our newest beta driver here:
http://beta.focusrite.com/releases/f..._usb2_drivers/
If these problems continue can you please contact our Support Team directly.
We may need to gather more info about your computer, which would be better done through our Support System, rather than on this forum.
http://focusrite.com/answerbase/contact
Best regards.