URI submitted has disallowed characters

[eluser]Angel Lay[/eluser]
It is worked before upgrading php 5.3.0

Codeigniter version is 1.7.1.

I tried :
[code ]
@ config .php
$config['permitted_uri_chars'] = '~%.:_\-';
[/code]

Code:

@URI.php
if ( ! preg_match("|^[\w".preg_quote($this->config->item('permitted_uri_chars'))."]+$|i", $str))

Any idea for that?
Thanks.