@elmezie You've read through the http://forum.mysensors.org/topic/1914/over-the-air-ota-bootloading-update-tutorial ?

Do you have something in your eeprom already blocking? Try clearing it using the provided ClearEprom sketch in examples.

@elmezie after a sleep the radio is not powered on again (sleep is for battery power nodes which normally do no expect message to receive) One can wake up the radio again by sending a message e.g. requesting a status or perhaps the current time with gw.requestTime(receiveTime);

Yes, it would be possible. But you won't save much juice as keeping radio in listening mode still requires way too much power to be able to run on batteries for any substantial time.