Magento Adminhtml override module not working

Stemming from my last question, I am stumped trying to do an override. I am doing exactly what MudithaE's answer here did, too.

I want to implement my own _prepareColumns() as found in the file app/code/core/Mage/Adminhtml/Block/Sales/Order/Grid.php. I set up my module's directories and the files as below. While researching, I saw a lot of developers like to do Dev_Module_Block_Adminhtml_blah, so I tried changing the directory structure and class names everywhere in my code. No change. My Cycleworks_SalesGridImproved module appears in the System -> Config -> Advanced listing, too.

Files: app/code/local/Cycleworks/SalesGridImproved/Adminhtml/Block/Sales/Order/Grid.php:

<?php
class Cycleworks_SalesGridImproved_Adminhtml_Block_Sales_Order_Grid  extends Mage_Adminhtml_Block_Sales_Order_Grid {
    protected function _prepareColumns() // tried public too
    {
                    parent::_prepareColumns();
        ...
        ...
        $this->addColumn('created_at', array(
            'header' => Mage::helper('sales')->__('Purchased On'),
            'index' => 'created_at',
             'type' => 'datetime',
             'format' => 'MMM d, h:mm a',
            'width' => '165px', 
        ));
        ...
        ...
        return $this; 
    }
}

app/code/local/Cycleworks/SalesGridImproved/etc/config.xml:

<?xml version="1.0"?>
<config>
    <modules>
        <!-- also tried: Cycleworks_SalesGridImproved -->
        <Cycleworks_Adminhtml>
            <version>0.0.01</version>
        </Cycleworks_Adminhtml>
    </modules>

    <global>
        <blocks>
            <adminhtml>
                <salesgridimproved>
                      <class>Cycleworks_SalesGridImproved_Adminhtml_Block_Sales_Order_Grid</class>
                </salesgridimproved>
                <rewrite>
                    <sales_order_grid>Cycleworks_SalesGridImproved_Adminhtml_Block_Sales_Order_Grid</sales_order_grid>
                </rewrite>
            </adminhtml>
        </blocks>        
    </global>

</config>

And in /app/etc/modules/Cycleworks_SalesGridImproved.xml:

<?xml version="1.0"?>
<config>
    <modules>
        <Cycleworks_SalesGridImproved>
            <active>true</active>
            <codePool>local</codePool>
        </Cycleworks_SalesGridImproved>
    </modules>
</config>

Please show me see what I'm missing... Thanks!

Update:

Just found out the extension EM_DeleteOrder is also overriding the same sales order grid class that I am. His extension's configuration is more complicated than mine, as his is set up to be called before the Mage core. The config.xml sure is busy!

<?xml version="1.0"?>
<config>
    <modules>
        <EM_DeleteOrder>
            <version>1.0.0</version>
        </EM_DeleteOrder>
    </modules>
    <global>
        <rewrite>
        <em_emadmin_adminhtml_sales_order>
            <from><![CDATA[#/admin/sales_order/#]]></from>
            <to>/emadmin/adminhtml_sales_order/</to>
        </em_emadmin_adminhtml_sales_order>
        </rewrite>

        <blocks>
            <adminhtml>
                <rewrite>
                    <sales_order_grid>EM_DeleteOrder_Block_Adminhtml_Sales_Order_Grid</sales_order_grid>
                </rewrite>
            </adminhtml>
        </blocks>       
    </global>
    <admin>
        <routers>
            <em_deleteorder>
                <use>admin</use>
                <args>
                    <module>EM_DeleteOrder</module>
                    <frontName>emadmin</frontName>
                </args>
            </em_deleteorder>           
            <adminhtml>
                <args>
                  <modules>
                    <EM_DeleteOrder_Adminhtml before="Mage_Adminhtml">EM_DeleteOrder_Adminhtml</EM_DeleteOrder_Adminhtml>
                  </modules>
                </args>
            </adminhtml>
        </routers>
    </admin>
</config>

Do you have any thoughts how I can use similar syntax and get my module to work and not have to hack his code? Like with an after="Mage_Adminhtml"?

Final Update: Sadly, the 3 answers below weren't the answer, it was the extension conflict. I'll answer my own question and mark it answered.

Solution

I'm answering myself, as this was a big lesson in extension conflicts and their resolution. Further, I learned a lot about our particular installation and how sloppy extensions can break everything.

As in the update, EM_DeleteOrder was overriding Adminhtml Block Sales Order Grid (absog). I also used the extension MDN_ExtensionConflict and while it wasn't detecting my exact conflict, it did show me that EM_DeleteOrder was using absog. I searched for extensions that would allow deletion of orders without using absog, which must be the easy way to go about it.

The extension Asperience_DeleteAllOrders manages to do this without overwriting the whole page and instead catches something in the router. Its config.xml is abstract art to me, so if you're an advanced developer, I think you'd appreciate his work more than I.

Ultimately, I found MageWorx_ExtendedOrders which replaces the entire absog with their own grid and has configurable additional columns. Included are custom shipping rates, order editing, deletion of orders, and order archiving. I am impressed with this extension for $149. I also am going through deleting the multiple extensions that were replaced with MageWorx_ExtendedOrders. I'm hacking their extension's code to put the columns in my desired order and to update the date format (and I'll share my changes with them as feature suggestions).