Persistent AirPort Extreme Connection Error Message

OK, thanks. That confirms that the external USB drive is not the server that is shown when you use the Finder > Go > Connect to Server command.

But you did mention that previously there was an AirPort Extreme on the network at one time and that it did have a hard drive connected. I still think that is the likely culprit.

If you have no idea what the existing server entry is for when you check the path above, the only thing that I can suggest at this point is to carefully write down the exact entry that is listed, then click on the entry to highlight it, then click the - (minus) button to remove that entry and restart the Mac.

If the connection error message goes away and everything else is working OK, then that was the issue.

If something that you normally use suddenly stops working, then you will have to reenter the info to get things going again.

If the error message still appears, I'm stumped. You will likely need to get a network guy out to the house to see first hand what is really going on.

You might not remember it, but chances are that at some point in the past you included the AirPort in the list of Login Items that load and open when you power up your iMac. If that is the case, the iMac is trying to start up and open the AirPort's drive or server, but cannot find it because it is no longer on your network. So, the iMac displays the message that you are seeing.......continuously.

Even if you could remove AirPort Utility from the iMac's operating system.....(you can't)......the message would still appear.

Please try the following:

Open System Preferences on your Mac

Click on Users & Groups

Click on the Login Items button just next to the Password button near the top of the Users & Groups window.

Does the AirPort appear in the list of items that will automatically start up when you power up or restart your iMac?

If yes, click on the AirPort listing to highlight it, then click on the - (minus) button at the bottom of the list of Login Items.

Close the windows

Restart your iMac

Then, another application......I don't know which one.......was programmed at one time to connect to the Time Capsule.

Are there any previous connections from the Finder to the Time Capsule? To check, open the Finder and click on the Go menu at the uppermost top of the screen where you see other menus like File, Edit, Help, etc.

Then click on the Connect to Server option to take a look at any previous connection paths.

It was an AirportExtreme and there was a backup hard drive connected

Good info and a strong clue.

Do you recall whether the hard drive that was connected to the AirPort Extreme was used for Time Machine backups, or other data storage?

If the hard drive was used for Time Machine backups, then Time Machine was programmed to connect to the hard drive for backups. Since the hard drive is no longer there, Time Machine cannot find the drive.

Or if the hard drive was used to store media files......music, video, images, etc......an application (iPhoto, Photos, iTunes, Music, etc) might have been set up to automatically log into the hard drive to use the media libraries stored there If that was the case, then the application is still looking for the hard drive but cannot find it because it is no longer there.

Regarding your penultimate comment:

a) There is one server address listed in the Server Address window (I've no idea what should be there if anything). Would that be my external backup drive?

Possibly, if your external drive is a network drive that connects to the network using an Ethernet connection. But, if your external drive is connected to your Mac using a USB connection, then that connection would not appear under the list of servers.

Did you have an AirPort Extreme or an AirPort Time Capsule?

If you had an AirPort Extreme, was there a hard drive connected to the USB port on the AirPort Extreme?