Problem with SharePoint Infrastructure Update can affect your extranet

This WSS KB article (KBID 951695, Last Review : July 23, 2008, Revision : 4.0) from Microsoft includes an acknowledgment of a known issue after installing the Infrastructure Update (32-bit, 64-bit). Applying the upgrade in a SharePoint farm that uses Alternate Access Mapping with a reverse proxy or a network load balancer, such as in an extranet deployment, may cause some public URLs to become unresponsive.

"Microsoft is aware of this issue and is developing a solution. Before installing the Infrastructure Update, customers who use this configuration should use a test environment to verify that public URLs remain accessible after the update is installed."

A few more details can be found on Joel Oleson's blog. Joel goes so far as to recommend that organizations using Alternate Access Mapping should hold off on the upgrade until a fix is available. I tend to agree, unless you are one of those rare companies fortunate enough to have a test environment with Alternate Access Mapping which mirror production.