Please use the "Uninstall" action in the AdwCleaner interface. It will clean older releases and avoid any error like this in the future.
Then, get the very latest release from there : https://toolslib.net/downloads/viewdownload/1-adwcleaner/
Regards,
fr33tux, 2016-04-12 17:17:30 (UTC)
Forgot to ask: why did this only happen that one time and never before or after?