NEVER ONCE changed any WINDOWS settings to allow access from a remote host
Again, I was talking about Win XP Firewall's File & Printer Sharing, not about the 323's. Since it wasn't my 323, I didn't (and still don't) know what sort of security walls might be in place. I didn't mean to imply that the 323 would be running XP, but it occurred to me that it might have a similar issue, and was not aware that they hadn't changed the gateway to point to their shiny new VPN router instead of the old non-VPN router - and probably wouldn't have even thought about it until it was mentioned. Thanks to you guys, when I called them and told them to check it - and they said "oops" and changed it - it was literally not more than a few seconds before it opened up.
As far as I know, the Win XP Firewall default on File & Printer Sharing is "My network (subnet) only", so if you're trying to map a drive from a computer on a different subnet (VPN or not), it's not going to happen unless and until you change that setting. I could surer'n hell be wrong, but that's what I've seen so far: different subnets, no map unless the default setting is changed.
Thanks again, I really appreciate the help.