Microsoft Knowledge Base Article 886185 contains the following summary:
This article describes critical update 886185. This update helps narrow the definition of the My network (subnet) only, or local subnet, scope option in Windows Firewall. This is helpful in situations where Windows Firewall would consider a large network to be on the local subnet because of how the dial-up software configured the route tables. After you install critical update 886185, you may have to restart your computer.