I know it works on Win 2K because we still have one 2k client here at my prem. It sounds to me that for some reason the scan data isn't getting to the core. If the device has the firewall up try shutting it down and then running the inventory. Maybe the client install didn't put in the exceptions for the Firewall? I know it sounds ridiculous but have you tried to refresh the scope on your console?
What happens if you take that saved scan file (it must be recent) and copy it into the ldscn folder on the core? Does it take it?