I knew what you meant. It freezes completely. Only a reset brings things back to life.
I have had this happen when I didn't connect grounds together and I have had it happen when I have put serial commands inside of interrupts (though it doesn't always freeze up.) What is the floatingpin thing you have read about?
The Dout voltage from the transmitter could be too high or too low. It should be held high when not transmitting. Do you have a multimeter to check it?