If some of your contacts are willing and capable to follow some simple instructions, you can try to use this tools: Ethereal (WWW dot ETHEREAL dot COM)

You would need to have it installed on their PC/Notebook, and will help you to take a network trace.

I used it a few time successfully while troubleshooting, and it might give you some additional clue of what is happening.

PS: The tools is free.

Edited July 16, 200916 yr by singa-traz

Thank you all, the problem has finally been found and fixed:

* As a security measure, the APF firewall blocks connections from reserved IP ranges by default.

* The authors of APF turned off automatic updating of the list (maintained by ARIN) in a recent version of the software.

* Over time, some of the formerly reserved IP ranges have in fact been issued and put into service.

* So basically the 'reserved IP' list on the firewall was out of date, and it has been blocking people using the recently issued IP ranges, thinking they were spoofed traffic.

The solution was simply to re-enable automatic updating of the reserved IP list in the APF configuration file. Now it all works again. Unfortunately I probably spent about 2 weeks chasing this. Argh!!!!

Thanks for your help.