An application that points to an intranet server is published in Microsoft Forefront Unified Access Gateway (UAG) 2010 Service Pack 2 (SP2). In this case, if a nonstandard HTTPS port is used, you receive an HTTP 500 error message when the application is accessed for the first time.
Note Access to the application is successful when the application is accessed again during the same client session.
This problem occurs because, when you connect to Forefront UAG, it stores the original URL that you tried to access before Forefront UAG redirects you through the Forefront UAG logon process. If you access a URL that corresponds to a published web application that is listening on a nonstandard HTTPS port, Forefront UAG cannot translate the internal Protocol:Host:Port combination correctly. This situation occurs in code that is called from StartApp.asp. This code only runs during the first request that a client makes to an application. Therefore, the problem does not occur on successive requests.
To resolve this problem, install the service pack that is described in the following Microsoft Knowledge Base article:
2744025 Description of Forefront Unified Access Gateway 2010 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates