Hey
I just look on the P2 code.
Find out this.
on inc/js.php #84
// Media upload script registered based on info in script-loader.
wp_register_script(
'media-upload',
'/wp-admin/js/media-upload.js',
array( 'thickbox' ),
'20110113' );
so, the file upload also need the thickbox js and the media-upload js
I guess u should include the two js code(thickbox and media-upload) in your theme header or footer
