I would first test the line by plugging in another computer through the wired connection. (Be sure to have a known "good" CAT-5/6 cable for swapping in.) If it doesn't connect to one of the wired ports on the router, most have a couple more that may be worth trying. It may tell you whether the problem is with the router itself, a cable, or the ethernet card on the computer.
It's generally a simple task to narrow down the specifics of this type of issue by swapping in known good replacements..
Hope this helps.
We have our home computers networked through a wireless router. One of the computers is not wireless and has always worked through this router (Linxsys WRT54GS) through the ethernet cable. We had a storm last week and everything went out (cable, internet, phone) We thought that our line had gotten hit but it turned out to be an area problem, anyway, the one computer that is linked to the main computer through the ethernet cable is now flashing between Local Area Connection is now connected and Local area connection A network cable is unplugged every few seconds. I have tried everything (except changing out the cables) and cannot get this computer connected again. I do not know if it would be a line damaged or a computer problem. The light for that computer is not lit on the router either anymore. If I am leaving out any information necessary, please let me know, I tend to be a computer dummy.