Windows Patch May Lock Users Out

A patch for Windows XP, Windows 2000 and Windows 2003 operating systems that is meant to fix a critical flaw, can lock users out, the windows installer service may not start, and more. Systems that have changed the default Access Control List permissions on the %windir%\registration directory may experience these and other problems.

On a computer that is running Microsoft Windows XP, Microsoft Windows 2000 Server, or Windows Server 2003, one or more problems may occur after you install the critical update that is discussed in Microsoft Security Bulletin MS05-051. These problems include the following:
The Windows Installer service may not start.
The Windows Firewall Service may not start.
The Network Connections folder is empty.
The Windows Update Web site may incorrectly recommend that you change the Userdata persistence setting in Microsoft Internet Explorer.
Active Server Pages (ASP) pages that are running on Microsoft Internet Information Services (IIS) return an HTTP 500 Internal Server Error? error message.
The Microsoft COM+ EventSystem service will not start.
COM+ applications will not start.
The computers node in the Microsoft Component Services Microsoft Management Console (MMC) tree will not expand.
Authenticated users cannot log on, and a blank screen appears after the users apply the October Security Updates.

The resolution is posted on this page discribing the problem, it just invloves changing the permissions on a couple folders as it has to do with your system not being able to access the COM+ catalog files.