Lost LAN

I run a LAN from a TP-Link wireless N router, connected by ethernet to a G5 Powermac tower with USB printers and an external Lacie hard drive, and by ethernet to a Devolo mains distribution LAN. I also use two laptops - an intel MacBook and a G4 iMac. This gives me, or rather gave me, full internet connectivity and full wireless connectivity between laptops, Powermac + USB printers and Lacie hard drive, until two days ago when mysteriously all contact was lost between computers. I still have internet access to all computers and I can still print wirelessly from the laptops to the printers which are connected by USB to the Powermac.

FileSharing is enabled on all computers.

I have tried with the Macbook, putting the Powermac's IP address into the server address field in Connect to Server but get the message "Connection Failed - the server may not exist or it may not be operational at this time." The same happens in the reverse situation on the Powermac.

Suggestions would be most welcome.

Correction - I THOUGHT filesharing was enabled on all computers! Somehow my PowerMac's filesharing had become switched off. It wouldn't switch back on again either, until I discovered some anomalies by running Verify Disc Permissions in Disc Utility. After I had Repaired Disc Permissions I was able to start filesharing again and now all is back to normal. Small pat on back!