Matt Quackenbush submitted this unusual behavior a few days ago and I was finally able to reproduce and fix today. Here is his excerpt:

If I browse to http://localhost/myApp/index.cfm/main/dspHome (or any other explicitly-called event), everything is good to go. However, if I browse to http://localhost/myApp/ or http://localhost/myApp/index.cfm, an exception is thrown that says:

The event handler: index.cfm.dspHome is not valid registered event.