Thks for answer. The check is out. I am going to try to explain a little better the problem.
The workstation has the firewall client for isa 2000.
When I try to enter this page,https://sib1.interbanking.com.ar/secureLogin.do?from=homesite, has or it does not have the firewall client enable or disable the browse this page is very very slow :(.
But if i enable in the Internet option-Connection-Lan Configuration-Proxy Server-Option advantage and configure the name and port isa server in http, Segure, FTp, and Gopher but not in socks and i have not check the "use the same proxy server for all protocols", has or it does not have the firewall client enable or disable the browse this page is normally.
In log Firewall sesion the only show me is:
10.1.51.142, -, -, -, 7/18/2006, 11:56:55, fwsrv, -, -, -, 184.108.40.206, 80, -, 0, 0, 80, TCP, Connect, -, -, -, 0, -, -, -, 42181, 1131260.
I hope that it has been possible to understand.