Hello
I have monitorized the connections between the proxy, the clients and
the domain server.
When in a client that works (only a small fraction) you can see the
squid machine talking to the PDC machine.
But if the client belong to the group that does'nt work, you can see
that no interaction occurs between proxy and PDC.
The requests reach the proxy from the client, but the proxy does not
authenticate it against the AD server.
it is not a load related issue as the proxy is only acceses by only one
client at once.
Regards
