I have debug mode on ( scriptMode="Debug" ), but my /extnet/extnet-init-js/ext.axd generates one long line of JSON, which makes it close to impossible to debug in the browser (e.g. create breakpoints in Firebug or Chrome's Inspector).

If the generated JSON could be well formatted / indented, it would ease browser debugging a lot.

Not sure if it will help you, but there are libraries available to reformat JSON, e.g. at http://dean.edwards.name/download/#packer

(As a workaround, is there any way for me to intercept the generated JSON and apply Dean's packer library myself?)