You need to install User Access Manager before but I installed it and UAM for NextGen don't work, I have two messages:
Notice: register_uninstall_hook was called incorrectly. Only a static class method or function can be used in an uninstall hook. Please see Debugging in WordPress for more information. (This message was added in version 3.1.) in /home/site/domains/mysite.com/public_html/wp-includes/functions.php on line 2959
Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/site/domains/mysite.com/public_html/wp-includes/functions.php:2959) in /home/site/domains/mysite.com/public_html/wp-content/plugins/si-contact-form/si-contact-form.php on line 1997
Somebody can help me?