Sounds like a defect interface IC or something within the network controller unit in your laptop.

>Yes, I think you are talking about the led showing on the tray bar (right bottom of the desktop). It says "unplugged" in my case, as if no network cable is plugged. And this is my problem; somehow the computer does not recognize that the cable is plugged. And I did test this cable on another computer (the one I am using now) and it works. But not on the other computer. I just can' imagine how it coule have changed overnight without me doing ANYTHING. I didn't install any new hardware, didn't make any changes, nothing. Puzzling.
>
>>Most PC's have one or to LEDs to indicate connection and/or connection speed close to the network connector, check whether they light up or not.
>>
>>>This is a laptop. But the problem I have is not with wireless but with the hard-wired networking.
>>>
>>>>If this is a laptop, it most likely has a switch to disable all wireless communication so that you can use it in a plane.
>>>>
>>>>>Hi,
>>>>>
>>>>>I was using my PC earlier today on a wireless network (at home) without any problems. I came in the office and plug in my cat5 cable but the network icon says unplugged. I tested the network cable on another computer in the office (on which I am typing now) and it works. But when I plug it into my " other" pc it does not work. In the Control Panel -> Networking, the network card does not seem to have any problems. That is, it says, "working properly"
>>>>>
>>>>>What else can I do to troubleshoot this issue? Maybe related or maybe unrelated, also this morning the cordless keyboard does not communicate with the computer.
>>>>>
>>>>>TIA for any suggestions.