Module interferes with admin ajax popups (assign stuff)

Hi,

I am writing a custom module and have experienced how trying to extend the oxbase class can interfere with stuff (I have managed to disable admin ajax popups - assign various stuff to various other stuff)…
Anyway, just to be in the clear: if I extend a core class, I effectively override its functionality with mine, so my class construct, where I have used init(‘mydbtable’) had the effect of unrelated oxbase objects trying to initialize with my db fields? Or?
And if oxbase is not overloadable, how can I cause such a havoc at all?
Confused…

a little more detail: i have the following metadata file:


<?php

/**
 * Module information
 */
$aModule = array(
    'id' => 'mymodule',
    'title' => 'Mymodule',
    'description' => 'Something',
    'extend' => array(
        'custom_order' => 'mymodule/custom_order_ext',
	'oxorder' => 'mymodule/core/my_oxorder',
	'oxbase' => 'mynewcoreclass'
    ),
    'files' => array(
        'custom_order' => 'mymodule/admin/custom_order.php',
	'my_oxorder' => 'mymodule/core/my_oxorder.php',
	'mynewcoreclass' => 'mymodule/mynewcoreclass.php',
    ),
    'templates' => array(
        'custom_order.tpl' => 'mymoduler/out/admin/tpl/custom_order.tpl',
    )
);


where custom_order is the admin view class, my_oxorder is the extension to oxorder, and mynewcoreclass is a class that is supposed to extend but not overload oxbase… Now, if I distribute these files into the system without separating them into a module, everything works fine. But as a separate module, things go wrong… Mynewcoreclass goes wrong… that is supposed to be a class like oxarticle, except it would handle data from my additional db table. Well, how do I register this class as a core class or what to call it, without implicating that I want to overload existing classes, like in the case of my_oxorder? Or do I have to just put it in the core folder after all?