Hello,
Thanks for your answer, I tested the temperature and there is nothing beyond 70ºC, so I don't know what's going on. The board works fine, only the ethernet is down. I've got a new Arduino Ethernet and loaded the same project with the same pin configuration and it's working perfectly (Controlling servos with OSC protocol).
I am using external power, a 9V battery which is not giving any problem with the new board, and seems to do the same with the old one (except with the ethernet).
Maybe the W5100 got burned and now is just not working properly? even if temperature now is "normal" and Voltage values are correct?
Thanks!