Images not displayed

Issue Summary

I have created a site using a virgin install fo D6.13 & image 6.x-1.0-beta3. However. when I create an image node the image simply does not display. Following the guidance at http://drupal.org/node/470724, I have
* cleared the Drupal database cache;
* public file handling;
* switched off core file upload module;
*disabled and re-enable image module, and watched as image content type disapperared and reappeared in in content type list;
*followed the advice at http://drupal.org/node/281115 and checked status report - which is all OK;
*checked admin/reports/dblog for errors - there were none;
*ChMOD'ed /sites/default/files/images/ and files to 777;
*manually browsed to image location http://mysite.com/sites/default/files/images/drupal.org_.png and this displayed the image in the browser;
*viewed the source for the image node and found the line <div class="content"><span class='print-link'></span><img src="http://mysite.com/sites/default/files/images/drupal.org_.png" alt="test" title="test"  class="image image-preview " width="264" height="84" />  </div>
*checked my server log - no entry found at time of image node rendering;
Can some kind soul please help me to solve this one - I really really want to use the great image and img_assist module on my site!