CKeditor not showing in IE 7

Hello,

I got a little problem with CKeditor.
CKeditor works fine in FF and IE8 but when I use IE7 it shows nothing.

It does create an text-area with an inline style: visibility hidden;
if I use the developer tools and change the visibility to block it shows a textarea with the content that should be in the editor.

the code that I'm using is:

<form method="post">
      Naam EN: <input type="text" name="title" style="width:150px;"><br />
      Naam NL: <input type="text" name="titlenl" style="width:150px;"><br />
      <br />
      <b>Engelstalig:</b>
<script src="ckeditor/ckeditor.js" type="text/javascript"></script>
      <script type="text/javascript">
         window.onload = function()
         {
            CKEDITOR.replace( 'FCKeditor1',
             {
               filebrowserBrowseUrl : 'ckfinder/ckfinder.html',
                 filebrowserImageBrowseUrl : 'ckfinder/ckfinder.html?Type=Images',
                 filebrowserFlashBrowseUrl : 'ckfinder/ckfinder.html?Type=Flash',
                 filebrowserUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Files',
                 filebrowserImageUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Images',
                 filebrowserFlashUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Flash'

             });
            CKEDITOR.replace( 'FCKeditor2' ,             
            {
               filebrowserBrowseUrl : 'ckfinder/ckfinder.html',
                 filebrowserImageBrowseUrl : 'ckfinder/ckfinder.html?Type=Images',
                 filebrowserFlashBrowseUrl : 'ckfinder/ckfinder.html?Type=Flash',
                 filebrowserUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Files',
                 filebrowserImageUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Images',
                 filebrowserFlashUploadUrl : 'ckfinder/core/connector/php/connector.php?command=QuickUpload&type=Flash'
             });
         };
      </script>
      <br /><br />
      <textarea name="FCKeditor1" id="FCKeditor1"><?=$contentNl?></textarea>
      <b>Nederlandstalig:</b>
<textarea name="FCKeditor2" id="FCKeditor2"><?=$contentNl?></textarea>
      <input type="submit" value="Toevoegen" />
   </form>