Local connection unplugged?

I am continually getting a message telling me the local connection is unplugged and/or there is an IP address conflict with another computer on this network. I have spoken to my computer guy who first told me it was my ethernet cable - which I have now replaced. However I am still getting this message. My computer guy has now told me it could be my NIC card. I am hooked up to a TP link wireless router and my laptop also loses the signal at the same time as my desktop does. Would it be my NIC card if I am losing connection on BOTH computers? Any advice at all gratefully received. I'm at wits end now and rubbish with computers. Is this easy to solve?