A PHP Error was encountered Severity: Warning Message: Cannot modify header

I would hazard a guess and say that you have called session_start() in your index.php file. Try searching for session_start() in your project.

A work-around is to modify the following file:

CodeIgniter_RCS/system/libraries/Session/Session.php

PHP Code:

// John added to try and see where the session_start() was already started
   if( isset($_SESSION) ) {
    // $TMP = $this->uri->uri_string(); // PROBLEM
    $TMP = $_SERVER['REQUEST_URI'];
    log_message('error', 'Session.php ALREADY STARTED: ' .$TMP); 

   }else{    
    session_start();

   }//endif;            

   // ORIGINAL SCRIPT
     // session_start();