While doing research on a different problem, I ran across this article: http://support.microsoft.com/kb/831138/en-us Would this be the reason why our web server is sometimes horrendously slow sometimes? All computers are Windows XP with the FWC installed, configured to use the proxy server in ISA2004. When it gets quite sluggish, I can disable the proxy settings in IE and access things at normal speeds again. If I do an IISRESET on the webserver, it also speeds up.