Q: Magento is adding Mage as class prefix when I access role permission in admin Fatal error on admission permission: Fatal error: Class 'Mage_Mypack_Mymodule_Helper_Data' not found in /path/to/magento/app/Mage.php on line 516
My config.xml
<?xml version="1.0"?>
<config>
    <modules>
        <Mypack_Mymodule>
            <version>0.1.0</version>
        </Mypack_Mymodule>
    </modules>
    <global>
        <models>
            <mymodule>
                <class>Mypack_Mymodule_Model</class>
            </mymodule>
        </models>
        <helpers>
            <mypack_mymodule>
                <class>Mypack_Mymodule_Helper</class>
            </mypack_mymodule>
        </helpers>
    </global>
</config> 

My admin.xml
<?xml version="1.0"?>
<config>
    <acl>
        <resources>
            <admin>
                <children>
                    <system>
                        <children>
                            <config>
                                <children>
                                    <mmmymodle translate="title" module="Mypack_Mymodle">
                                        <title>Mu module permission</title>
                                    </mmmymodle>
                                </children>
                            </config>
                        </children>
                    </system>
                </children>
            </admin>
        </resources>
    </acl>
</config>


A: <mmmymodle translate="title" module="Mypack_Mymodle">

should be
<mmmymodle translate="title" module="mypack_mymodule">

Also, you should check if your module is enabled or not. (app/etc/modules/Mypack_Mymodule.xml)
