DS18B20 causing arduino to "hang"

So I've got two shiny new DS18B20's which are outputting what they are supposed to now, however they seem to be causing the ardiono to hang. I don't know if its initialisation that's the problem, but most of the time the arduino just doesn't want to know and doesn't even want to output anything on the serial port. It seems to run setup and gets no further. If I load a few other sketches into it, eventually it comes back to life and I get some output. Otherwise though it just hangs doing nothing. If I remove the protoshield though with the DS18B20 on it everything works fine. Any ideas?