JDispatcher: :register: Event handler not recognised. Handler: Array

I am getting the following error after updated to latest Joomla 2.5 version in 3 of my sites

error_log:
mod_fcgid: stderr: PHP Warning: function_exists() expects parameter 1 to be string, array given in /public_html/libraries/joomla/event/dispatcher.php on line 101
mod_fcgid: stderr: PHP Warning: class_exists() expects parameter 1 to be string, array given in /public_html/libraries/joomla/event/dispatcher.php on line 107
mod_fcgid: stderr: PHP Notice: Array to string conversion in /public_html/libraries/joomla/methods.php on line 342