A likely possibility is a bad card or interface. A jabbering card can mess everyone else up on that switch, (I know the switch is supposed to limit where the frames go, but I have seen this happen). A flakey interface or connection can cause errors for all packets passing thru it.
Can you substitute another switch? This would help isolate the problem to the switch or the clients/cables. Some of the newer cheap switches have a tendency to accumulate errors, even with minimal traffic. We had this with our internet connection. We used a new 5 port switch to link the firewall to the external router. Within a month, our ISP called me to say his router was accumulating errors. It turned out to be the cheap switch.
If the problems are more wide spread you may want to check out the configuration of the topology.
Are the switches and hub managed?
Do the failures have a pattern linked to the topology? For example, if you are having problems with a system on the hub talking to a system on a switch, you may have issues with speed and duplex. Hubs work only at half duplex and most switches want to run at full duplex. Make sure your switch to switch links are set to 100 Mbit full duplex on both ends. Make sure the switch connection to the hub is running at half duplex.
The clients are more likely to connect correctly automatically but check them anyway.
We had some reliability issues on our network and when I tracked it down, I found a cisco switch talking half duplex to a bay switch running full duplex and a cisco running full duplex to hp switches running at half duplex. When I matched everything up instead of letting them “negotiate” the connection, the errors went away.