Yun - impossible load scketch - Ubuntu 12.04 as Guest Virtualbox


I have spent all the day trying to send my scketch from the IDE (in an Virtualbox guest ) to my Yun card.

It was working fine for an Uno, through /dev/ttsy0, as well as through USB connection.

But it doesn't work for my new card, a Yun (neither through /dev/ttys0, nor through /dev/ttyACM0) . From the host (under win 7) It's working fine through USB.

When I try to send the scketch for the first time after I have booted the VM the RX LED blink few time, then the red LED (L13) rapidly flash... that's error message...but nothing happens .. the scketch is not loaded in the card. After that first test every attempt fails (no LED error effect on the card...)

Another clue : at the booting time the RX LED blink from time to time. When the guest is fully started, simple commands like "echo "z" > /dev/ttys0" produce the RX Led reacting... After trying to upload the scktech the "echo" command doesn't blink the RX LED anymore...

Do you have an idea ?