I have always used Firebug (a firefox extension) to debug my javascript applications.  However, it appears that the Dojo 1.0.x libraries load javascript via AJAX mechanisms.  Firebug does not support the debugging of JavaScript that is loaded via AJAX.

Luckily there is a workaround.   There is another firefox extension by the name of fireclipse that patches firebug to handle this situation.

It can be downloaded and installed from here: Fireclipse

Additional Configuration:
1. Go to the “Script” tab inside Firebug
2. Open the “Options” menu located near the right side of the window
3. Select the following: “Show eval() sources”, “Use Last Line for eval() names”, and “Decompile scripts from Source”