Sorry, been a little too busy to post.
I am using just back up to disk at the moment. The biggest problem, as I already mentioned, I have run into is that Backup Exec appears to overwhelm the USB buffer and literally, the disk just disappears as far as the system is concerned.
The only way it seems to recover from this is to cancel the job or have the system cancel it. You then either have to reboot the disk by switching it off and on, if it hasn't been running too long or as an emergency, reboot the Server (not a good idea from a user perspective).
I've now installed a firewire card in the server and a new external disk enclosure with a firewire interface. However, the problem seems to still occur and if anything, that interface appears even flakier than the USB one.
As an alternative, I've wondering if it would be worthwhile backing up to an internal disk and then copy the backup files to the external disk. This is a bit of double handling but I'm hoping it will at least leave me with a complete backup!
I'm presently running Windows 2003 server, Backup Exec 9.1. The server itself is something my predecessor decided to cobble together out of bits and pieces (this bloke took three months to build this POS and as he was a toolmaker in an small engineering works, made his own case, disk mounting blocks and ventilation system!), essentially its a P4 3 Ghz system with 2 MB of RAM, Serial ATA disks, Promise RAID card. It works, but only just as I'm finding out.