 <p>When you changed from classic pipeline to integrated pipeline, you essentially turned control over to .NET, meaning .NET will call up the ASP Parser. This adds the ability for custom HTTPModules coded in .NET Managed code that can change the output of the response or in the case of elmah, give you logging details.</p> <p>I would look at the log, see what user agent <a href="http://www.useragentstring.com/pages/Googlebot/" rel="nofollow">googlebot</a> is using at the time when the error occurrs and follow the exact same path it did with your user agent changed.</p> <p><a href="http://www.mozilla.com/en-US/firefox/new/" rel="nofollow">Mozilla Firefox</a> is the best browser for this with the <a href="https://addons.mozilla.org/en-US/firefox/addon/user-agent-switcher/" rel="nofollow">User Agent Switcher</a> addon</p>