did you try a system restore to the last time it was working properly just in case some how the settings got changed?

Have you tried a different ethernet cable? and plug into a different port in the router?
Those are some things I would try.
I assume you did try the repair for that network connection?

Yes, I tried a system restore which "took" (now my AV definitions are out of date). There is only one port on this router; it is a Cradlepoint 350 cellular router since I use Verizon 3G service for my internet connection. Yes, I also tried the repair and it did nothing. I do have a Netgear router wired to the Cradlepoint and then another cable from Port 1 to the desktop. I'll try changing that to a different port. If it works, I'll post back immediately. Right now I do not have any extra ethernet cables, but if I can't get things going, I'll certainly get another one or two.

You might try uninstalling the ethernet adapter and rebooting to reinstall.

Try repairing the connection first.
Start - Settings - Control Panel - Network Connections.
Right click on the wireless and select 'Repair'. If you don't notice the caches being cleared on the 1st pass, run it again.

Other things to try if above instructions fail,

Go to Start > Control Panel - If you are using Windows XP's Category View, select the Network and Internet Connections category. If you are in Classic View, go to the next step.

* Double-click the Network Connections icon.
* Right-click the Local Area Connection icon and select Properties.
* Highlight Internet Protocol (TCP/IP) and click the Properties button.
* Be sure Obtain DNS server address automatically is selected.
* OK your way out.

Go to Start > Run and type in cmd
Click OK

* This will open a command prompt.
* Type the following line in the command window:

ipconfig /flushdns (note the space between ipconfig and /)

* Press Enter on the keyboard.
* Exit the command window

Restart your computer.

No Go,

Boot the computer to Safe Mode w/ Networking and see if you can connect there.

All is now working. Here is what I did: I removed the ethernet cable connecting the Cradlepoint router to the second (Netgear) router, and connected it directly to the computer. I really believe that the cable from the Netgear router to the computer is faulty, so I will buy another one. I use the Netgear to give the wireless signal a wider range than the Cradlepoint provides.

Zep, I checked the TCP/IP properties, and it was not checked to Obtain DNS server address automatically. Instead, it had the ip address of the Cradlepoint router entered. I changed it, following your instructions, and kept losing the connection, so I put the setting back as it was. I think there is a reason I had it that way. I am using Open DNS on the router, and I think the instructions were to set it up that way. At any rate it is now working, so I'll leave well enough alone. Oh, yes, the wireless is working also.

Thanks to everyone for your suggestions.

Just wanted to let you know that I reconnected my router(s) as I previously had them, but using a new Cat5 Ethernet cable in place of the suspect one. Everything is working perfectly, so, RC, once again you "hit the nail on the head."

Glad that you solved the problem Grandms!

very good news! I tell you sometimes it is the easy things that stump us! I have had some bad cables and bad connectors so now that is one thing I check.

Great news that you were able to figure it out. It's exactly the same problem I had on my wired desktop recently, which turned out to be a disconnected cable. I have had a myriad of issues working wirelessly, but the only wired issues I've ever had were related to the cable itself. Cheers!