Hi, I have google many times about this error. I haven't found any definitive answer about how to fix this stupid error permanently. So often, I can upload code smoothly for a long time, then out of the blue I get this error. I restarted the arduino, re-paired with the Mac, reboot the Mac.. Nothing works. What the hell causes this error? What exactly caused this problem? Is there a bug in the Arduino IDE? A bug in the firmware or what? Does anyone have a permanent solution? I use OS X buy the way.