While creating node,, if node being created is selected as natural language, other than listing, prevents adding other languages.
Workaround is

  1. to tell users to select one.
  2. hack to refuse code

First one is hard to implement, thus the second workaround is to change modules/translations.module at line 78 there is 

function _translation_tab_access($node) {
  return !empty($node->language) && translation_supported_type($node->type) && node_access('view', $node) && user_access('translate content');
}

change remove the "!empty($node->language) && " condition. the final view should:

function _translation_tab_access($node) {
  return translation_supported_type($node->type) && node_access('view', $node) && user_access('translate content');
}