Thanks to all those who suggested SOCKINFO.NET.SYS
This turns out to be very usefuol - it allowed us to find out who the
"client" was, and to ask them to be a little more "nice".
However, this poses another question.
If the client has gone away (for what ever reason), and the server program
is still there with the sockets open (don't know if the sockets really WERE
open, we had to reboot the box, <gasp>), is there anything I can do to write
a utility to convince, persuade, bully the server to get the heck off my
system, so I can do backup?

Or do I go with Pete Crosby's comments that this was probably a race to
release a semaphore. (If so, how can I detect semaphore locking?)

Inquisitive minds want to know (they say that if I find this out, I can go
home and get some rest - yeah!

TOny "zzzzzzzzz" Furnivall