Users drive mappings disappear

We are running Netware 4.11 SP9.

Users will start complaining that their drive mappings have disappeared, then when someone tries to log in, they can’t. This is then often followed by the server freezing and having to be power cycled to restart it. Sometimes I can shut it down cleanly other times the shutdown process will start, get as far as shutting down the router and then it freezes.

I have checked all the logs and there are no entries written to any of them about the time this happens. As the server does not abend, no abend log is created.

The only application running on the server is Symantec anti-virus but this is configured to only perform overnight scanning and does no on Access scanning.

Any ideas on the cause?

Jonathan