Can't use $wpdb->update inside a page

Hi

I can’t interact with the database when editing pages! I can use php but DB interactions cause page to stop at the point where $wpdb->update is called. Any ideas?

Thank you

[insert_php]
$emember_auth = Emember_Auth::getInstance();
echo $user_id = $emember_auth->getUserInfo('member_id');
//Shows 54
$update_data = array('first_name' => 'g');
$where = array('member_id' => $user_id);
$wpdb->update( 'wp_wp_eMember_members_tbl', $update_data, $where, $format = null, $where_format = null); //Breaks here
[/insert_php]