Forms in Thickbox

I tried to put one of my forms into a thickbox, but no success.
I found out, that I have to enqueue the scripts for the form - done in header.php just before wp_head (). Still no success : the conditional logic does not work at all but I can use simple forms and i.e. upload images from the thickbox form.
Here is my code:

<?php if ( is_singular() ) { wp_enqueue_script( 'comment-reply' ); }
	gravity_form_enqueue_scripts(20, FALSE);
	gravity_form_enqueue_scripts(21, FALSE);?>
<?php  wp_head(); ?>
<?php $theme->hook('head'); ?>

and

<input class="thickbox" title="Feld für den Titel" type="button" value="Wartungs-Menü" alt="#TB_inline?height=700&width=400&inlineId=examplePopup1" />
<!-- </div>-->
<div id="examplePopup1" style="display: none;">
<h2>Wartungsmenü</h2>
<div style="float: left; padding: 10px;"><img src="http://shibashake.com/wordpress-theme/wp-content/uploads/2010/03/bio1.jpg" alt="" width="150" height="168" /></div>
Erläuterungen für das Wartungsmenü
			  <?php
/*			   print do_shortcode('[gravityform id="20" name="Test-Formular attachments"]');*/
			   gravity_form(20, false, false, false, '', false);
			   ?>
			   <strong>Ausserhalb klicken um zu schliessen..</strong></div>

I am using WP3.3.1 de_DE and GF 1.6.1.
I can't figure out what's wrong? Can someone help, please?

Yes and no!
No, in terms of this approach: I used "form lightbox plugin" by myphpmaster.com and this solved above problem.
Yes in terms of another form I try to setup. The form is more complicated having a tinyMCE-Editor in a textarea activated through a HTML field. This textarea ( and the editor) are non-reactive when showing in form lightbox.
I am not very sure where the problem is : tinyMCE, GF or form lightbox plugin.
On the other hand, I am still hoping to get a wp_editor solution for textareas in GF pretty soon. This might solve the whole issue anyway. Any hope?

I am doing this on my site. Try using the Easy FancyBox plugin then set your link up like this example:

<a title="Contact Us" href="#fancyboxID-1" rel="nofollow">Ask a Question</a>

Then you need to add this code to page...

<div style="display:none" class="fancybox-hidden"><div id="fancyboxID-1">[gravityform id="1" ajax="true"]</div></div>

Of course change your gravity form id number to match your form. You can see an example on my site http://flatfeerealty.com/contact/ then click the button in the left box.

Here is a link for reference http://websitesetuppro.com/how-to-open-gravity-forms-form-in-a-lightbox/. Hope that helps you out.