Yeah, I now agree, I'm inclined to think the problem is with us, as I've just tested it on:
NS4.08/W95 (works)
NS4.7/NTSERVER (works)
NS4.7/NTWKSTATION (not woking yet, but I'm sure it will)
Tomorrow I'll test on other S4.7/NTWKSTATION machine in other offices and get back to you.
Thanks H for all your good work...