[p4] Cannot delete user

[Marshall, Tony [CIB-IT]]

I want to delete a user from Perforce, but Perforce reports that the
user has opened files. However, it also reports no pending changes for
the user.
 
e.g.
 
> p4 user -d -f <user> 
User <user> has file(s) open on 1 client(s) and can't be deleted.
 
> p4 changes -s pending -u pg50976
(no pending changes displayed)
 
So how do I delete the user?
 
Tony