After you apply Microsoft Internet Security and Acceleration (ISA) Server 2006 Service Pack 1 (SP1), the Firewall service (Wspsrv.exe) may crash intermittently.
Additionally, the following events are logged in the Application log:This problem occurs when the caching functionality is enabled and when there are content type-based rules.
This problem occurs because of an issue in ISA Server 2006 SP1. After you apply ISA Server 2006 SP1, ISA Server may incorrectly handle a response that is served from the cache when content type-based rules are being used. This issue can cause the Firewall service to crash.
To resolve this problem, apply hotfix 956269.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
956269 Description of the ISA Server 2006 hotfix package: July 28, 2008
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