Airport, AppleShare and Printers (URGENT

I have an airport with 5 iMac clients. Everything has been running well for 2 years. Recently the iMacs are losing the internet, printers and appleshare. A reboot of the clients sometimes brings the internet back but never the printers or appleshare. Sometimes resetting the base station is the only way for the clients to re-connect to the internet. Does anyone know why the iMacs aren’t able to see the printers or other computers on the network? I can connect to other machines directly using IP addresses. Our printers don’t have IP addresses if that helps.