The file became corrupted about 3/4 through the process. I have re-ran the automated procedure on other machines with similar results. once I got an error: File "" not available. But there was no filename specified. So far this has been an isolated incident.

The machine it is running on:
2000 pro
500mgz
40GB HDD 50% free space
256 MB ram
Recently defragged and rebooted.
THe machine has been running for about 2 years, performing this same task.

The network is 100% 100BT, server has a gigabit port.
NT4 SP6
I tweaked the MTU to 1454 which is typical to 2000 boxes, as per http://www.dslreports.com/faq/5793 .
All switches, no hubs.