Home network issue

[Shadow_Walker]

Just moved to Sky and have a strange issue. If I move files locally from computer A to computer B the internet cuts off, can't ping the router etc and can't get online but the files still copy locally. As soon as the files have finished copying it immediately starts pinging the router again.

 

Any ideas before I dig deeper?

[FishCustard]

Are A and B connected to the Sky modem/router/everything-box, or is there a switch involved?