I think I found the problem. I think it misbehaved because of an illegal character in the "HOSTNAME". Changed the hostname yesterday and It was still alive this morning even if I have not pinged it.
Really interesting, maybe I could build something cool around the Arduino HeatpumpIR (https://github.com/ToniA/arduino-heatpumpir) library I've been building. Right now I'm integrating it with Domoticz (http://www.domoticz.com/forum/viewtopic.php?f=34&t=7179#p69647).
I'm an ex-Microsoft employee from Finland (resigned about a month ago).
