Bad ethernet port?

Well here we go:

The background - Bought my friends tower from him when he moved to Canada. He used wireless internet with it. I haven't had a computer in my room (hooked up to this exact ethernet cord) but I have had this ethenet cord hooked up to a ethernet connector and had another cord hooked up to my 360.


The problem - I am randomly dropping internet connection and just a quick unplug of the ethernet cable from the tower and plugging it back in fixes the problem and I'm back up and running. I never had this issue with the 360 though.


I'm not totally sure what could be wrong, any ideas?

 

duplicate IP addresses on the network, device on the network with the same IP as the router, network card is going bad.

 

Is there anyway to diagnose the problem?

 

If it's the network card it's going to be tough. I had this problem in the office and chased it for months. Called in the professional techs and they chased it for a while too. I added another network card and it helped some. In the end it was actually caused by a program but it's not a program worth mentioning, I doubt more than 3K people in the world use it. I think it was a combo of all of the printers and scanning devices and that program.

network cards do go bad. I used to keep at least one spare in the office for all the times i had to change one out. Haven't had it happen as much in recent years. I would search that model of network card and see if it's a common issue for it to go bad. A replacement network card isn't too bad of a repair.