I have this router sweex LW055 and I have fixed all this problem with the new firmware apr-m14h-v1158en.lfi from the website
http://alonline.eu/. It is a different model, but use the same firmware and this fix all the problems with the WAN connection, so you don't need to use any trick for the configuration. I hope that this help to all the people that have problems. Good luck
