Novell server lockup during arcserve backup

Abend 1 on P00: server….Kernel detected an attempted context switch while holding a spinlock
-this is the error that halted the server.

Other symptoms:We have a new NW6.5SP2 server,
that abends during backups during the night.
The abend however is never exactly the same from one time to the next when the system halts from an error. Mostly during the Arcserve backup we have problems. The abend occurs after
12 to 15 gigs of data have been backed up.

These errors are frequent and restarting the server is necessary regularly 3-4 times a week. Any ideas for a workaround or solution?