Sorry, my mistake. I mis-remembered how the debug window works (I was certain there was an option to view this).
What about running your program and clicking the "trace" button in the message window just prior to invoking whatever calls the parent script handler, then unclicking the trace button so you're not overwhelmed with info. That, once you wade through it, might help narrow it down.
As far as your second issue goes, perhaps you could "watch" the variable and gain some insight into when it is initialised.