HttpModule IIS6 Default Content Page

I have written c# .net 4 HttpModule to change image paths.  I am using IIS6.  The code will work if I there is a page name in the url ex: www.site.com/Default.aspx.  If the url doesn't contain a page name like: www.site.com and has a default content page (IIS6 | Documents | Enable default content page | Default.aspx), I get an error: 

Server Error in '/' Application.

The resource cannot be found.

Is my only option to do a app.Context.RewritePath?