I found a way to debug javascript, in case something more powerfull is needed:

The how to is described here: http://www.jonathanboutelle.com/mt/archives/2006/01/howto_debug_jav.html

The download is here: http://www.microsoft.com/downloads/details.aspx?FamilyID=2f465be0-94fd-4569-b3c4-dffdf19ccd99&displaylang=en