I understand, but it's much more difficult to troubleshoot when I can't reproduce the problem. I should have verified that you are using the most recent version of the plugin (current stable is 0.9.3.3). Download the latest version of the plugin: http://wpcctm.com/cctm-dev.zip. There was a similar issue with version 0.8.9 (see this ticket), so make sure you've upgraded.
What is the path to the broken images? Also, are the paths broken on the page that lets you define the custom field, or only when all possible custom-fields are listed?
Most of this comes down to the get_custom_icons_src_dir() function inside of includes/CCTM.php. Many other bits rely on that one function
Hope that helps.