Can not insert link to image in fckeditor

Thank you for the IMCE module. I am testing IMCE with fckeditor and trying to insert an image with a link to another image. eg thumbnail to full size image. I presume that the correct way to do this is to click on the insert/edit image button on the fckeditor toolbar and to select the thumbnail image first in the image info tab and then in the link tab (within the same image properties dialog box) click on the browse server button and locate the full size image that you wish to link to. When I do this, nothing appears in the url field on the link tab, but the url in the image info tab is overwritten with the new selected image. This occurs for me on my drupal 5 beta 2 test site and also on your demo site.

Thanks in advance for your help.