I had to override adminhtml controller class (Mage_Adminhtml_System_ConfigController) with my module’s controller class (MyNamespace_MyModule_ConfigController).
It was really tough to find the right solution. I googled, searched in magentocommerce forum and found a lot of solutions. But they didn’t work for me.
After searching & trying more, I got some work done with the following piece of code:-
<global>
<routers>
<adminhtml>
<rewrite>
<system_config>
<to>MyNamespace_MyModule/config</to>
<override_actions>true</override_actions>
<actions>
<save>
<to>MyNamespace_MyModule/config/save</to>
</save>
<index>
<to>MyNamespace_MyModule/config/index</to>
</index>
</actions>
</system_config>
</rewrite>
</adminhtml>
</routers>
</global>
But this gave “404 Error Page not found” when I go to System->Configuration.
Finally, I did the controller override with the following code:-
<global>
<rewrite>
<mynamespace_mymodule_config>
<from><![CDATA[#^/admin/system_config/#]]></from>
<to>/mymodule/config/</to>
</mynamespace_mymodule_config>
</rewrite>
</global>
Hope this helps. Thanks.