It can't be your central, system.log I don't know..
Did you tried to see on the firewall ??
Or maybe if you have a brother or sister, who use the same one for another IP, it happened to me, and I have changed the "Puerto UDP 4321" from my IP, because 2 IP's can't have the same "Puerto"
After that I don't really know, I wish I helped you. If not you will have to wait Manutoo's answer.