Can't find server with internet connection.

Directly above the DNS server info you will see the router ip. (Something along the lines of 192.168.x.y) Enter these numbers, exactly as you see them, into the DNS server space. So those numbers will appear twice.

Now click on Apply, close the window, and check if the internet connect is working.

Does your Mac, running OS X, even see the router?

If the Mac does see the router, I suggest you go ahead and setup the router, starting from scratch. The setup process is a matter of following instructions on the screen.

To get to the router setup from the Mac, open your browser, and in the browser url field type in the router ip. If your mac sees the router, this will get you to a window that asks for user name and password. The router manual tells you the default (which of course you can change) for these two items. When you enter the correct name and password, you will see a screen that will walk you through the process of setting up the router.

More than one computer can simultaneously communicate with the server.

Try a different cable between your problem iMac and the router.

You have already told us the imac connects in OS 9. I made the suggestion to try a different cable in full awareness of that. If this were my problem, I would try switching cables.

Do your computers see each other? Set up file sharing and verify if the two computers can share files.

Do you have an utility called "Internet Connect"? Came with 10.4 and (I think) 10.3. Try running it.

I strongly recommend you reset your router, and set up your connections all over again. Instructions for resetting the router should have been supplied with the router.

http://discussions.apple.com/post!reply.jspa?threadID=1190431#
Have been reading through this discussion and found it to be a repeat of my morning. I have also completed all the steps listed..even changed the cable. The ISP said the IP address is the problem. Gave me the correct address but it won't stay in the system. Keeps reverting back to the incorrect address. The IS tech said the number which begins with 169 is an error message of some sort. Any ideas.

OTA,

The previous discussion involved two computers, a router and a modem. Could you please describe your set up, viz. the hardware being used to connect to the internet, and the OS on your Mac.

When a modem keeps generating an incorrect IP, the problem is often in the modem. In that case the first thing to try is resetting the modem. However, this is just a guess since you have not provided enough information about your set up.

The external modem is a Motorola SB5120 Surfboard. I Mac G3 OS 10.4
But here's a bit of info from the kids (I was at work). Early yesterday morning there was a lightning strike, very close, very loud. No connection after. The computer works fine and the ISP tech gets a ping back on his end but there is no connection between the two. Surge protector in place.

Since the problem is between the Mac and the modem, I'd try a different cable between the two. Sometimes just turning the cable around, i.e. putting the end that is in the computer into the modem and vice versa, could help. But if one of the connectors (either on the modem or the computer) is fired, this will not help. Have you examined the connectors?

By the way, are you connecting via ethernet or USB between Mac and modem?