Slow Arcserve bkup of Dell 705N NAS svr

We are using Arcserve 2000 advanced edition on an NT4.0 server to backup (over the LAN) a Dell PowerVault 705N NAS server. We are getting backup speeds of only 6MB/min avg.

When using the NTBACKUP utility backup speed is 44MB/min avg.

Any ideas on whats causing Arcserve to be so slow and how to speed it up.

Thanks in advance for your help.