Warning: Illegal offset type in /var/www/wordpress/wp-admin/admin.php on line 99

Warning: call_user_func() [function.call-user-func]: First argument is expected to be a valid callback in /var/www/wordpress/wp-admin/admin.php on line 99

line 99:         call_user_func($wp_importers[$importer][2]);

working example of print_r($wp_importers)
Array
(
    [textpattern] => Array
        (
            [0] => Textpattern
            [1] => Import posts from a Textpattern Blog
            [2] => Array
                (
                    [0] => Textpattern_Import Object
                        (
                        )

                    [1] => dispatch
                )

        )

)

The $wp_importers that is causing the error:
Array
(
    [phpnuke] => Array
        (
            [0] => Phpnuke
            [1] => Import posts from a PHPNuke Database
            [2] => Array
                (
                    [0] => Phpnuke_Import Object
                        (
                        )

                    [1] => dispatch
                )

        )

)

they're exactly the same from what i can tell.

from import/textpattern.php (working example and basis for phpnuke importer)
<?php 
...
class Textpattern_Import {
...
}

$txp_import = new Textpattern_Import();
register_importer('textpattern', 'Textpattern', __('Import posts from a Textpattern Blog'), array ($txp_import, 'dispatch'));
?>

from import/phpnuke.php (new file)