Images uploading but not appearing when published - solved

Hi,
I've just installed FCKeditor in Drupal and having a problem with images. I can edit a page, upload an image to the server, then insert it into the page and it appears there in the Drupal editor window. But when I preview or publish the page, all the content appears except for the images, not even placeholders are shown. If I then edit the page, I can see the images again in the editor window. Any ideas what might be wrong? Many thanks in advance for your help.