network hangs

I have an interesting problem. the problem began last Tuesday at 12:20pm. It happened again on Wed at 5:00pm, Thurs at 6:00pm, and monday at 10:50am.

The network hangs, many workstations lose sessions to our HP3000 server and network programs they are running off of NT servers lock up.

And our NOVELL server locks up with an abend: Page Fault Processor Exception
Error code 00000000
Novell Netware 4.1
Running process: Interupt Service Routine
Interrupted process: Server 02 Process

The network hung again today, but our novell server didn’t crash. Could the novell abend jam the entire network? or is something else jamming the network? and how do I begin to troubleshoot?

thanks
elang