I was configuring ISA Server for a client, and ran into an interesting issue. It made sense once I realized what the error was. I was creating two rules, 1 for IP:80 and one for IP:8080. It was the same IP, but there was an app running on 80, and another app running on 8080.
HTTP 502 status error with the message "The URL does not use a recognized protocol, Confirm that a valid protocol is in use (for example, HTTP for a Web request)"
I was having some issues (see above), and after looking at the event logs, I noticed the Event ID: 14148.
The Web Proxy filter failed to bind its socket to <XXXXXXXX> port <XXXX>. This may have been caused by another service that is already using the same port, or by a network adapter that is not functional.
To make a long story short – you can’t publish a rule in ISA for an IP that is using port 8080. ISA considers it ‘special’.
For additional info, read this TechNet Article: http://technet.microsoft.com/en-us/library/bb794799.aspx