why npc does not work ? who can help me?

[wfj]

I have installed the npc module for cacti,but it does not work ,why,could you tell me?
the follow is the environmet:
(1) php
cacti:/var/log/apache2 # rpm -qa | grep php
php5-mysqli-5.1.2-29.5
php5-devel-5.1.2-29.5
php5-5.1.2-29.5
php5-gd-5.1.2-29.5
php5-snmp-5.1.2-29.5
php5-mysql-5.1.2-29.5
php5-mcrypt-5.1.2-29.5
php5-pdo-5.1.2-29.5
apache2-mod_php5-5.1.2-29.5
php-json is "php-json-4.3.2_1.2.1-1.aurore.src.rpm"
(2) apache
cacti:/var/log/apache2 # rpm -qa | grep apache2
apache2-example-pages-2.2.0-21.2
apache2-2.2.0-21.2
apache2-doc-2.2.0-21.2
apache2-mod_python-3.1.3-60.2
apache2-devel-2.2.0-21.2
apache2-prefork-2.2.0-21.2
apache2-mod_php5-5.1.2-29.5
apache2-mod_perl-2.0.2-14.2

(3) nagios,ndo,and cacti are work properly.

the following is error_log of apache2 when I click the npc button.
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[Wed Oct 22 22:28:50 2008] [error] [client 10.37.5.209] PHP Warning: reset() [<a href='function.reset'>function.reset</a>]: Passed variable is not an array or object in /srv/www/htdocs/cacti/lib/functions.php on line 146, referer: http://10.37.192.47/cacti/settings.php?tab=npc
[Wed Oct 22 22:28:50 2008] [error] [client 10.37.5.209] PHP Warning: Variable passed to each() is not an array or object in /srv/www/htdocs/cacti/lib/functions.php on line 147, referer: http://10.37.192.47/cacti/settings.php?tab=npc
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