ASP.NET 4.0 URL routing 404 problems with IIS7

As I described before, I love the new routing feature in ASP.NET 4.0.  I succesfully converted my code from Intelligencia over to the built in routing.  The site ran great locally, but when I deployed to IIS7, I got 404's on every page that didn't have an extension.  Those pages were my routed product pages.

Some googling led to to add a line to my web.config file.  Here is is:

<system.webServer>
    <modules runAllManagedModulesForAllRequests="true" />
  </system.webServer>

This apparently forces IIS to invoke the routing module.  I found no mention of this anywhere and was under the assumption I didn't have to modify any config files.  Hope this helps somebody.

Here are some sources where I found this:

http://forums.asp.net/t/1523639.aspx
http://weblogs.asp.net/scottgu/archive/2007/02/26/tip-trick-url-rewriting-with-asp-net.aspx