This might sound rather weird. On my X61 (running Windows 7) whenever I connect a network cable to its Ethernet port, its status will quickly blink over to "Identifying..." before switching back to "Network cable unplugged" again. I've tested the cable and the router with another laptop and it works fine, so the fault is probably with this particular machine.

I've also tried using a dock's ethernet port instead to see if it is something related to the physical port on the laptop, to the same effect... so chances are the actual network card is busted. Can it be? I've never encountered a bad network card before. Could it be some other BIOS setting that I've missed out on?

There isn't a separate card for Ethernet on the X6X series. The Gigabit Ethernet is integrated into the systemboad (motherboard). What happens if you run another OS, like a Linux Live CD?

Great tip! After I've booted up from a Ubuntu LiveCD, it worked. And a subsequent reboot into Windows works too... so it is probably just some weird thing going on

Gah. Seems like it happens intermittently... my guess is that somehow it can't receive an IP address via DHCP.

It happens intermittently in both Windows and Linux?

Yeah. I'll try to hunt around my room for a spare cable and report back again. The cable has lost its "click" so that might be the cause, but even when I hold the connector by hand to the port, it still does the same thing...

And weirder still, other machines don't have that problem using that very same cable.

Sorry to resurrect an old thread, but I'm now having the same problem on my X220. What was your resolution? Was it a hardware or a software issue?

In my case, it works fine at home, but fails at work. If another computer is connected to the same port (with the same cable), it works fine. I don't think I'm getting an IP address correctly. I reinstalled the ethernet adapter, made sure all settings are default, did a netsh resest...no help.

You probably run W7. Check this article: http://www.windowsnetworking.com/articl ... ation.html

Thanks, RealBlackStuff. I do run W7 Pro, and tried the troubleshooter, etc. Nothing seems amiss in settings; it just keeps cycling through Enabled --> Identifying... --> Network Cable Unplugged. But only at work! Works fine at home.

SmallWalrus said via PM that his was a hardware issue resolved by a mobo replacement. Since it works at home though, I find it hard to believe that it's a hardware problem in my case...I could do a system restore or factory reinstall, but that's a pain.

I'll check with IT here at work, maybe call Lenovo tech support, and report back.

If you use Access Connections, disable it and let Windows manage connections.
Maybe your (software) firewall prohibits access at work?

I think ours are different problems

I ruled out the OS being the cause by booting up under Ubuntu. No go there either. That helped me conclude it was the chip on the motherboard.

I tried a fresh install (ugh) and the problem persists. IT at work will be looking at it soon (maybe after Thanksgiving) and we'll see from there. The mystery continues!

Tell me about the network? DHCP? Domain controller? Do you have another machine connected? If so, what are the settings?

Thanks for the input. IT came to check it again. The jack and cable work fine with other computers, and my computer still won't connect even running Linux. So it looks like a hardware issue; I'll put in a call to Lenovo.

Conclusion: I had the system board replaced, and it works fine now. So, it was the same problem as OP. Thanks for all the support!