try this one.It may help you as its working for me.
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php/$0 [PT,L]
put the code in your root htaccess file.and make sure that you have
$config['index_page'] = '';
in your config file.
Please let me know if you face any problem.