يه مشكل دارم تو Isa Server 2004

سلام به همه
من يه شبكه دارم كه هم lan , هم wan . كه ايتژنترنت اون از طريق يه مودم HDSL تامين مي شه .
توي ISA يه اشكال داره اينترنت وصل نمي شه

Alert Information
Description: Web Proxy service failed to bind its socket to 172.17.1.30 port 80. This could be caused by another service that is already using the same port or by a network interface card that is not functional. The error code specified in the Data area of the event properties indicates the cause of the failure. For more information about this event, see ISA Server Help.

و اينم ارور توي اينترنت اكسپلورر:

500Internal Server Error - The parameter is incorrect.(87
Internet Security and Acceleration Server)