I've been doing a few big overnight copies over the VPN, using XCOPY,
and it will run fine for hours and hours then mysteriously give up,
saying the remote drive is no longer working or something like that - I
will write down the exact wording when it happens next. But the VPN
remains up, the drive mappings are still good and all I need to do it
start copying again and it works fine.

Any idea as to what might be causing this? NW65SP5UPD1, VPN client is