Codeigniter 2.1.2 Disallowed Key Characters

Following up this thread well it just happened that my ci 2
application won't load up and only showed me "Disallowed
Key Characters" on screen. Arrghhhh... hate to say this but
the only way i got this fixed is to modify the core!

Go to your %system/core/Input.php and find
"if ( ! preg_match("/^[a-z0-9:_\/-]+$/i", $str))".
Modify it to
"if ( ! preg_match("/^[a-z0-9:_\/-\|]+$/i", $str))".
It stops showing me the disallowed key error.

Anyway right before i touched the core, had tried
to add the "|" char in to %application/config/config.php.
But nothing seems to be happened and error screen
still showing.

Hope it helps.