ethernet has a self assigned IP-address and may not connect

Try a different cable or disconnect the cable that goes to the Windows PC and use it with the MB. Use the original MB cable with the Windows PC. If the Windows PC now can't connect, the cable is bad. Is the router configured to only accept devices that it already knows the MAC (hardware) address for?

Having the same problem with my g5, says its got a self assigned ip and doesnt connect to the internet, but i can go online with my 360 just fine using the same ethernet cable, if you work out the problem, anypne, let me kno

You might have MAC filtering on your router, access point, or modem. Check to make sure that MAC filtering is disabled (or add your Mac's MAC to the "accepted" list).

I have the exact same problem!!

FIX IT APPLE FFS!

That's MAC = Machine Address Code (I think), not Mac as in Macintosh Computer. Every computer has a MAC code, it's an ID number for that computer. The router can be set up to only allow specific MAC codes on it's network, thereby keeping out any machine not on the list. There is a way to spoof this code if you're a serious hacker, but for the most part it will keep the average joe from stealing your bandwidth.

Go to your networking preferences and click on the the network you're using (Airport or Ethernet)

You should see a hex number like 00:17:f2:44:03:85 (yours will be different) listed as the Airport ID or Ethernet ID

Go to your router setup page and see if you have MAC Address filtering turned on. Turn it off and see if you can connect.

Message was edited by: Adrift

I have the same issue on my Mac Pro. It happens regardless of which cable, router or even internet service I try. I had no problems with Tiger, but Leopard is dead in terms of internet connectivity. There are several other threads around here pertaining to similar issues- some claim success by editing the DNS IPs, which I tried, and it worked for a little bit, but the problem returned shortly thereafter.

Mac Address filtering is for wireless only on my router so it can't be that...

I have exactly the same problem. My G4 was working fine with my Netgear DG834G router. Yesterday it would not connect to the router after startup. Restarting the router, the G4, and using the Network Diagnostics app finally got me connected, and it was fine all night. Today, nothing I try will get the G4 to see the router. It cannot connect via the ethernet or the wireless network (though it accepts the WPA key and connects to the router, still no IP address). It's driving me up the wall. I've tried deleting all the network preferences I can find, but still no joy.

My Macbook, running Leopard 10.5.1, works fine via the wireless connection.

I have at least found a solution that allows me to connect to the internet. I used the Address Reservation service of my router to reserve a specific IP address for the MAC address of the G4's ethernet port. Then I entered all the IP addresses manually in the Network Preference Pane (IP address, subnet mask, router address), including using manually assigned DNS server addresses (OpenDNS servers in my case).

Now at least the network is working correctly, and as I never move the G4 I can at leave it that way until Apple release a fix. But it does seem that something in the DHCP setup is broken in Leopard.

I hope that helps people having similar issues.

Go into Macintosh HD/Library/Preferences/SystemConfiguration
delete (com.apple.airport.preferences.plist/NetworkInterfaces.plist/preferences.plist) . Do not empty the trash yet. Restart the computer. You will need to reconfigure your network location in system preferences/network on how you connect but that is easy. If everything works now then you can empty the trash. I have tried this and it works fine. I hope that apple will fix this to because I have had to do this twice.