Help.. could not upload any sketch anymore !

After I plugin and power up the Arduino Yun, it was recognized in my Mac book pro. When I open Arduino studio,
the port is also list there.

After I press the upload sketch, it hangs for a while, the give me error saying Port not available..

After I power off and back on again, the ports become available. It seems uploading the sketch broker my USB/serial connection.

Anybody seen this behavior before??

Yes sometimes happen also to me.

need reboot couple times