Where as, the module reflected this error message in the Kunena Forum Component’s activity stream:  

Warning: mb_substr() expects parameter 3 to be long, string given in public_html/libraries/phputf8/mbstring/core.php

The fix for this very annoying Kunena error was a simple configuration modification. If you are experiencing this issue with the Kunena Forum Component, then contact AdverGroup Web Design so that we may troubleshoot your Joomla website and remedy your error. We can solve this issue for Kunena Latest 1.7.1, Kunena Latest 2.x and Kunena Latest 3.x.