I thought I'd add this to my previous reply. I'm guessing that your computer is going to "sleep" because of your computer settings & not because of a fault with the cable or the program. I think you can prove this by unplugging the cable while the program is running and you will get a message that the cable can't be found, but it will not put your computer into the state that you have described. Screen saver & power saver settings often activate because of inactivity. They must "see" activity from the mouse or keyboard to keep them from activating. I don't believe activity through the usb port (your transmitter) will satisfy them. If you have these features activated and don't want to disable them, I suggest that you move the mouse about every 5 minutes and it will reset the count down timers. I hope this helps.
Crowfly