Windows Defender Update and the Page Error in Development Web Server

Another of the strange, unexplained errors with a simple (yet unexpected) cause.

SYMPTOMS

You are developing an ASP.NET Site or Web Project in Visual Studio 2005/2008. You start the Debug process. Your browser window opens with a message:

Page Load Error

or

The page cannot be found.

Additionally, you have Windows Defender installed on your machine.

THE CAUSE

A flawed update of the Windows Defender removes the localhost entries from hosts file in windowssystem32devicesetc folder.

SOLUTION

Manually add the following entries back to the hosts file:

127.0.0.1 localhost

More details: http://www.h-online.com/security/Windows-Defender-False-alarm-triggered-by-hosts-file--/news/112814