$this->addAttribute('customer_address', 'customer_type', array(
    'attribute_set'		=> 'attribute_set_code',
    'type' => 'varchar',
    'input' => 'multiselect',
    'backend' => 'eav/entity_attribute_backend_array',
    'label' => 'Customer Type',
    'global'            => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_STORE,
    'visible' => 1,
    'required' => 0,
    'user_defined' => 1,
    'visible_on_front' => 1,
    'option'            => array (
        'value' => array('1' => array('1'),
						 '2' => array('2'),
						 '3' => array('3'),
						)
    )
));



liegt in Model

<?php

class Rw_Intrashipprint_Adminhtml_Model_Customertype
{

    /**
     * Options getter
     *
     * @return array
     */
    public function toOptionArray()
    {
        return array(
            array('value' => 1, 'label'=>Mage::helper('adminhtml')->__('Yes')),
            array('value' => 0, 'label'=>Mage::helper('adminhtml')->__('No')),
        );
    }

}


Source model "" not found for attribute "customer_type".