First experiences with Venkman

Yesterday was my first trial of Venkman with Seamonkey; I seem to be
bedeviled by cockpit or environment problems.  Having loaded an HTML
page (from the Venkman demo, no less), and then started Venkman -
about 75% of the time nothing was displayed in the "loaded scripts"
pane - though the "loaded files pane" did display the name of the
loaded page.  No scripts means no debugging ...

Reloading the HTML page (view.reload, etc), restarting Venkman,
closing all browser windows and starting over, etc had no effect.
Then out of the blue, "loaded scripts" is now populated and I can
actually use the debugger.  So I go to bed thinking everything is
fine.  This morning things are completely non-functional again -
nothing displayed in "loaded scripts" - and I can't discover the magic
procedure to fix it.

OK - so I switch over to Firefox - works fine right out of the box.
Except: once I exit the debugger, I can never get it to activate again
without reinstalling it (via drag-n-drop).

Really feels like environmental problems - but I don't know how to
sleuth this.  Help would be much appreciated.

My environment:

Win XP Pro, SP2 + all available updates
Seamonkey: 1.1.1
Firefox 2.0.0.2
Venkman: 0.9.87

Browsers were installed without Venkman.  The latter was then added
with drag-n-drop installation.