If this error occurs sporadically or at busy times, it probably means that the network is saturated. Wait for network traffic to clear. If bottlenecks arise frequently, think about reconfiguring the network or adding subnets.
Another possible cause of this message is a noise source somewhere in the network, such as a loose transceiver connection. Use snoop(1M) or a similar program to isolate the problem area, then check and tighten network connectors as necessary.