I am doing this in Magento 1.9 CE. So my objective is to log out the user as soon as the password is changed.

1. I registered my extension at app/etc/modules/Bmg_Golo.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Bmg_Golo>local</Bmg_Golo>
        <active>true</active>
    </modules>
</config>

2. My config.xml is at app/code/local/Bmg/Golo/etc/config.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Bmg_Golo>
            <version>0.0.1</version>
        </Bmg_Golo>
    </modules>
    <global>
        <models>
            <bmg_golo>
                <class>Bmg_Golo_Model</class>
            </bmg_golo>
        </models>
    </global>
    <frontend>
        <events>
    <controller_action_postdispatch_customer_account_resetpasswordpost> 
                <observers>
                    <bmg_golo>
                        <class>bmg_golo/observer</class>
                        <method>logout</method>
                    </bmg_golo>
                </observers>
    </controller_action_postdispatch_customer_account_resetpasswordpost>
        </events>
    </frontend>
</config>

3. I created an observer at app/code/local/Bmg/Golo/module/Observer.php

<?php
class Bmg_Golo_Model_Observer
{
    public function logout($observer) {
        $session = Mage::getSingleton('customer/session');
            if ($session->isLoggedIn()) {
                Mage::getSingleton('customer/session')->logout();
            }
    }

}
?>

My customer logged out after changing the password. I doubt the event/observer in the config is wrong and my method in the observer is not getting called. Please help me as I am new to magento.