debug XUL in a Thunderbird 3 extension with venkman

Hello,

I have now read a lot of pages and searched a long time. I have found
"Debugging a XULRunner Application" under "https://
developer.mozilla.org/en/Debugging_a_XULRunner_Application" but was
not able to get the venkman window with start_venkman().

I can start the venkman addin over Menu/Extras/JavaScript Debugger but
it don't display any thing of my extension.

I have inserted <script src="chrome://venkman/content/venkman-
overlay.js" /> inside the window tag of the the main xul file of my
extension. Additionally I have a new button inserted with:

<hbox class="box-padded">
    <button class="wizard-button" dlgtype="extra1" id="venkman"
label="venkman" oncommand="alert('hallo'); start_venkman();"/>
    <spacer flex="3"/>
    <button class="wizard-button" dlgtype="back" id="back"
label="&back.label;" disabled="true" oncommand="back();"/>
    <button class="wizard-button" dlgtype="next" id="forward"
label="&forward.label;" nextval="&forward.label;"
finishedval="&finish.label;" oncommand="next();"/>
    <separator orient="vertical"/>
    <button class="wizard-button" dlgtype="cancel" id="cancel"
label="&cancel.label;" oncommand="close();"/>
</hbox>

If I start my extension and click on the new button 'venkman' the
alert box appear but venkman don't start after.

I have unziped venkman under C:\Program Files\Communication\Mozilla
\Thunderbird\distribution\bundles\venkman.