>Nobody has change anything.. We use here the software PROXY+.. Please do you know how can I do it ?

We've seen big corporations that were off the scope by receiving our main page version dated two weeks old. Then, they sent us emails asking why it was never changed. Then, later we realize that their proxy was not well configured. Some of them did intentionnaly cached pages on their proxy for such time. Can you imagine that? That means that anyone from that company were always two weeks outdated for wherever they were surfing. So, that could cause some of that.

As you have used another connection and that worked, that seems to be related to something similar. At this point, I can't help as I don't know that much about it but I would simply show your sysadmins that it works in one way and not in the other. So, it would then be up to them to figure it out.