Arduino Due - Error after upload, No device found on COM

HW:Arduino DUE R3 SW: IDE 1.5.5, Interface: programming port, Win7

In the beginning everything worked fine. In the next moment after upload the Blink sketch, I get the error message "No device found on COM6". And that's where I'm stuck. Has anyone else had this problem? The COM interrface look ok and was already new installed.

Is USB programming port mapped as COM6? When Due is unpugged, is COM6 still present? Did you try to restart the computer? Did you try to erase Due? Did you try the loopback test?

And there is not anything that helped you? http://arduino.cc/en/Guide/ArduinoDue