Network connectivity problems

For some reason one of our Netware 6.5 sp7 servers started having network connectivity problems. This just suddenly appeared when users returned from a week holiday. Connection to this server is hit and miss. I can ping other servers both Netware and SLES OES, and Windows from this server but pinging workstations is hit and miss. I can ping workstations from the only other Netware server on the network no problem. I switched to a different nic and switch port and changed cables. Still the same. Any ideas?