Hi Max,
Vizard first looks in the local directory of the script, then it looks in the Vizard20/plug-ins directory. Do you have an older version of the plugin in your local directory? I've placed the latest 5dt plugin in a zip file on our webpage. You can download it
here This is the same file that came with the 2.17 installer, but maybe the old version wasn't overridden. Just place this file in the Vizard20/plug-ins directory. Let me know if this helps.