I got a call from work Friday night - after troubleshooting the problem, it appears that the 'fixed' backup client on the W2K server is making backups just fine, but really chewing up the network while doing so. After we changed the default reconnect port on it, it now reconnects fine, but it is doing so at such a rate that it is generating 25-40% lost packets and retransmits. Not good. When a 100mb pipe gets so full of malformed packets and retransmits that 10mb clients get kicked off of the network, and thus cause the critical applications to fail... Mucho Not Good.
We get to revisit this Monday, wish me luck.