Problems starting the JavaScript Debugger - Venkman

Hi,

I'm using Mozilla version 1.7.12 and Venkman version 0.9.81 on a WindowsXP 
machine.  This is my first time trying to debug JavaScript using the Mozilla 
Platform, and the Venkman JavaScript debugger.  I have a simple JavaScript 
that gets executed when a XUL window loads, using the onload event.  The 
JavaScript is in a seperate .js file, and is included into the XUL file.  I 
start Mozilla with the -console switch, and then start Venkman and press the 
big red X in the upper left had conner, and it displays "...".  From reading 
the FAQ this means the debugger will stop on the next JavaScript instruction 
executes.  I then switch back to Mozilla, do a File->Open File and open my 
XUL file, and no break points are hit.  This even happens when I load the 
.js file into Venkman, and set a "Future Break Point".  However, when I look 
at the Mozilla console I see this:

<top>
anonymous@54
jsdExecutionHook@262
onxblpopupshowing@157
[anonymous]@0
vnk: execution hook: function onxblpopupshowing(event=Event:{0}) in 
<chrome://gl
obal/content/bindings/popup.xml> line 156
** ASSERTION FAILED: stopped in a filtered URL **
<top>
anonymous@54
jsdExecutionHook@262
onxblpopupshowing@156
[anonymous]@0
vnk: execution hook: function onxblpopupshowing(event=Event:{0}) in 
<chrome://gl
obal/content/bindings/popup.xml> line 156
** ASSERTION FAILED: stopped in a filtered URL **
<top>

And this seems to repeat a whole lot.  Can anyone help me understand what is 
going here, and what I can do to start debugging JavaScript in Mozilla using 
Venkman.

Thanks,

-Frank