Magento Tabs – Add Content Under Additional Information

What you should be able to do is using the following xml set the template of the view tab:

<adminhtml_customer_edit>
    <reference name="customer_edit_tab_view">
        <action method="setTemplate">
            <template>your/template/file.phtml</template>
        </action>
    </reference>
</adminhtml_customer_edit>

You'll need to do a little detective work. It's very possible a different change is responsible for the error you're seeing, or that something about your replacement triggers this error.

To start, I'd remove any custom functions you have in Mymodule_Customer_Block_Adminhtml_Customer_Edit_Tab_View and concentrate on getting the class rewrite working without a Wrong tab Configuration exception — that way if the error is tied to a method you've added, you'll know which one when you add your methods back one by one.

The exception you're seeing comes from this method

#File: app/code/core/Mage/Adminhtml/Block/Widget/Tabs.php
public function addTab($tabId, $tab)
{
    if (is_array($tab)) {
        $this->_tabs[$tabId] = new Varien_Object($tab);
    }
    elseif ($tab instanceof Varien_Object) {
        $this->_tabs[$tabId] = $tab;
        if (!$this->_tabs[$tabId]->hasTabId()) {
            $this->_tabs[$tabId]->setTabId($tabId);
        }
    }
    elseif (is_string($tab)) {
        if (strpos($tab, '/')) {
            $this->_tabs[$tabId] = $this->getLayout()->createBlock($tab);
        }
        elseif ($this->getChild($tab)) {
            $this->_tabs[$tabId] = $this->getChild($tab);
        }
        else {
            $this->_tabs[$tabId] = null;
        }

        if (!($this->_tabs[$tabId] instanceof Mage_Adminhtml_Block_Widget_Tab_Interface)) {
            throw new Exception(Mage::helper('adminhtml')->__('Wrong tab configuration.'));
        }
    }
    else {
        throw new Exception(Mage::helper('adminhtml')->__('Wrong tab configuration.'));
    }

    if (is_null($this->_tabs[$tabId]->getUrl())) {
        $this->_tabs[$tabId]->setUrl('#');
    }

    if (!$this->_tabs[$tabId]->getTitle()) {
        $this->_tabs[$tabId]->setTitle($this->_tabs[$tabId]->getLabel());
    }

    $this->_tabs[$tabId]->setId($tabId);
    $this->_tabs[$tabId]->setTabId($tabId);

    if (is_null($this->_activeTab)) $this->_activeTab = $tabId;
    if (true === $this->_tabs[$tabId]->getActive()) $this->setActiveTab($tabId);

    return $this;
}

And occurs when Magento can't instantiate a tab from information passed into addTab. My guess is your error comes from this bit of layout XML in catalog.xml

<action method="addTab"><name>customer_edit_tab_view</name><block>customer_edit_tab_view</block></action>

Although adding some temporary debugging to the addTab method above will help with that

var_dump($tabId, $tab);

If that's the case, it sounds like Magento may be having trouble instantiating your new block class. I'd try running the following code

$block = new Mymodule_Customer_Block_Adminhtml_Customer_Edit_Tab_View;
var_dump($block);

$block = Mage::getSingleton('adminhtml/customer_edit_tab_view');
var_dump($block);

and looking for instantiation errors (each call should return a block object).

My best guess as to why this is happening is you have your View.php file for Mymodule_Customer_Block_Adminhtml_Customer_Edit_Tab_View created in the wrong folder.

Good luck!