Wrong "delete request" link in og_content_type_admin_block_details block

You should add user uid in order to make it work. Replace

$links[] = l(t('delete request'), "og/unsubscribe/$node->nid", array(), 'destination=og');

with

$links[] = l(t('delete request'), "og/unsubscribe/$node->nid/$user->uid", array(), 'destination=og');