Restarted, the Network cable unplugged?

I restarted my comp this morning at the office and now it says that my network cable is unplugged. I tried to swap out my 3COM NIC card with a Realtek one, but I received the same error. Any ideas to why this would happen? I dont think its the cable but they are run throughout the building and are inside the walls.

 

I really hate that particular error. Not sure how it should be phrased but basically the real meaning is

This is your PC speaking. I know we have a network card and I know it is supposed to connect to a network. However, just now it is not and I'm not sure why.

Possible causes
- almost certainly NOT your network card except in the very unlikely event that all of it is working except the external socket the network cable is plugged into.
- could be a physical cable problem. Within a building there could be rodents or construction or a cable that was always marginal and got wiggled just a tiny bit and failed. Again, probably not.
- could be a hardware failure of the slot in the hub or switch at the other end.
- could be a speed/duplexing mis-match between your NIC and the hub/switch port. A partial failure at the other end can cause this.

The most frequent causes I find when a user gets this error are
- the user moved some equipment and either damaged the cable connector or else plugged it in the wrong spot
- the network infrastructure folks did some work and didn't get things back the way they needed to be.

Impossible to diagnose from a distance and tough to do without testing equipment even for someone on site. If you have local support, get them involved.

About the only things you can try now that you've found out that it isn't the NIC are
- to manually set speed & duplexing to see if a different one works. The card is very likely set to auto so start with 10Mbps half-duplex and keep increasing until you find out if any combo will work. Probably only two speeds and for sure only two duplexing options so it won't take long.
- to check the wall plate connection if your building is set up that way. Sometimes unplugging and plugging back in will do the job.