Buil-in Ethernet has self-assign IP adress


Something happened recently with my PPC G5. Mac cannot to establish internet connection and in System preferences/Network i can see next :"Built-in Ethernet has self-assign IP address." Also in Network pane i can see that it has no router address and wrong subnet mask. To connect it uses DHCP. When i switch DCHP to manual and back and then restart Mac at login it asks to allow accept incoming traffic for AppleVNCServer.bundle, configd, nmblookup, mDNSResponder. Then i have connection to the net and in Network pane its says "Buil-in Ethernet is currently active and has IP address........" Also the router address and subnet mask becomes proper. It happens every time i turn on computer. Any suggestions?