The Microsoft Firewall service on a Microsoft Internet Security and Acceleration (ISA) Server 2004-based computer may stop responding. Additionally, you may find events that resemble the following in the Application event log:
Note In the previous event, %number is a placeholder that represents the value of the parameter name.
Note In the previous event, xxxxxx is a placeholder that represents the address.
This problem occurs if the following conditions are true:
The client tries to access the ISA Server to cache responses to client requests.
The size of the file that the client requests is larger than 64 kilobytes (KB).
The client tries to access the same file and the ISA Server sends an "If-Modified-Since" request to the Web server.
The Web server responds with an HTTP status code "304 Not Modified" message to the file request.
The ISA Server sends the requested file from the cache, and then tries to delete the cached file.
Under these conditions, the Web proxy service may stop responding.
To resolve this problem, install the hotfix package that is described in the following article in the Microsoft Knowledge Base:
916106 Update for HTTP issues in Internet Security and Acceleration Server 2004 Service Pack 2