Codeigniter error 404 on production after set_flashdata - codeigniter

Question

I'm using CI on my project, when I moved it on production server, I saw the error "404 page not found" when calling $this->session->set_flashdata. This error is preserved when I requested any page until I cleared the cookies. This error repeats after call "set_flashdata" again.
function _set_success($message)
{
$this->session->set_flashdata('is_db_msg', 1);
$this->session->set_flashdata('db_msg', $message);;
}
$result = $this->page_model->edit_page($page_name, $this->_get_data_array());
$result ? $this->_set_success('OK') : $this->_set_error(DB_ERROR);
redirect(BASEURL.'admin/pages');
// server 404 (on any page) after redirect
BASEURL it's constant: DEFINE('http://mysite.com');
Also I'm using this .htaccess:
DirectoryIndex index.php
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^www [NC]
RewriteRule ^(index\.php/?)?(.*[^/])/?$ http://mysite.com/$2 [L,R=301]
RewriteCond %{HTTP_HOST} ^www [NC]
RewriteRule ^$ http://mysite.com [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(index\.php/?)?(.+)/$ /$2 [L,R=301]
RewriteCond %{ENV:REDIRECT_FINISH} ^$
RewriteRule ^index\.php/(.*)$ $1 [L,R=301]
RewriteRule ^(main/index(/index)?|index(\.php)?)/?$ / [L,R=301]
RewriteRule ^([^/]*)/index/?$ $1 [L,R=301]
RewriteCond %{REQUEST_URI} ^(system|application).*
RewriteRule ^(.*)$ /index.php/$1 [L,E=FINISH:END]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ /index.php/$1 [L,E=FINISH:END]
Please, help and sorry for my bad english.

Answer 1

You should use following for redirecting:
redirect('admin/pages');
or
redirect(base_url().'index.php/admin/pages');
or
DEFINE('BASEURL','http://mysite.com')
redirect(BASEURL.'index.php/admin/pages');