Unfortunately there isn't any logging for scripts right now. The only real way to debug them is to install the IE browser plugin that is part of WebPagetest (stand-alone installer for the plugin is here - http://code.google.com/p/webpagetest/dow...akechanges ) then if you go to tools->AOL Pagetest a new window will open and you can tell it to run a script.
Ive got a similar issue with a script using click action.
Ive tried it with AOL Pagetest Plugin and it worked. (Well, at the end after some seconds Waterfall window is refreshed with a blank screen, but at least click action is executed)
If I try it with webpagetest.org I am running into timeouts or my scripted click event is nt executed.