You must say what computer you have. Open Device Manager and see what network cards you have. For instance, some computers have an ethernet card and a wireless card. If you use wireless and the ethernet card is enabled, you will always see that message. Disable it in Network Connections and it will go away.

Computer is XPS/Dimension XPS Gen 5.  Three devices listed as network adapters. Broadcom NetXtreme 57xx Gigabit Controller, two 1394 Net Adapters. It looks like original configuration sheet identifies the 1394 as "Card (circuit), Multi-media, Audio, 1394, SB0358". No wireless NIC installed on this computer. I've tried disabling the 1394 adapters with no effect. I've also tried disable  one of the 1394 adapters with no effect. I rebooted and the second 1394 adapter was recognized and automatically reinstalled. 

       I also tried installing a USB wired adapter with the NetXtreme disabled. Same result.    

       I connect to my high speed ISP (cable modem) with Vonage Linksys router. My laptop connects to the router (wireless and wired) without a problem. Same cables tried on both desktop and laptop.    

      I did install Dell's network assistant on the Desktop (it's now unistalled) but problem (cable not connected) was occuring before then.

Did this just start to happen out of the blue?  CAn you relate it time wise to something you did (new software or hardware for example)? 

 

You've tried all different (new) cables, different ports on router, USB network adapter.  Have you recycled the router and modem then tried again?  Have you tried turning off ALL firewalls (XP firewall, software firewall, a/v firewall/worm protection)?   

 

If your problem is intermittent then it becomes more difficult to diagnose.  Did you have any spyware or malware that was removed recently?

 

The issue is whether it's hardware or software.  SOme other simple things to try would be to set your onboard nic to 10mb/s, reboot, and see.  Or try a new pci nic card, they're cheap.  You could try rebuilding tcp/ip stack but not sure that is the issue.

JFK I had the same problem. Just spent $25 and install a pci nic card. Go to bios 1st and disable inergrated one. Solved my problem.