Hmm that\'s weird. Works fine for me.
What version of PHP is on your site?
http://uk.php.net/manual/en/function.str-replace.php
mixed str_replace ( mixed search, mixed replace, mixed subject [, int &count])
and the line in question is:
[php]
$urlwww = str_replace( \'www.\', \'\', $_CONF[\'site_url\'], 1 );
[/php]
Which is search, replace, subject, count as specified in the docs.