I have a primary computer that is allways on the problem is that MJ keeps shutting down by itself. The MJ soft phone is always on the screen and the computer does not enter hibernate mode. Also MJ will shut down at any point weather I am using the computer or not.
.
Maybe your USB port is losing power or having power cut off by the computer for power saving. Make sure the USB port for the magicjack is configured so that the computer can't turn it off. Try putting the magicjack on a powered USB hub might also work.