Merci beaucoup pour la réponse, canadien.
Unfortunately, changing the battery has been the first thing I did, to no avail.
Two different batteries did not succed in reviving that belt... D*&Y$$.
As for the bricked watch, I'll try and contact the german guy, thank you. Anyway paying extra money for a failure depending on the watch malfunction makes ma bit agry, as I said previously.
Thanks again and have a good time,