Possible explanation for error and site crashing randomly without any provocation?-Collection of common programming errors

I have a multilingual client that “suddenly and randomly” started suffering errors and a site crash.

The client assured us they “have not touched the site since it went live.” And, more or less we can confirm that given that we have not updated the site on their behalf, as we are the the only ones with update privilages.

Has anyone had their multilingual site “just randomly crash” after months of being live with no problem?

This is the error message. Has anyone seen this before?

WD php: PDOException: SQLSTATE[42S22]: Column not found:
1054 Unknown column ‘ml.language’ in ‘where clause’:

SELECT ml.*, m.*, ml.weight AS link_weight FROM {menu_links} ml
LEFT OUTER JOIN {menu_router} m ON m.path = ml.router_path
WHERE  (ml.menu_name IN (:db_condition_placeholder_0, :db_condition_placeholder_1, :db_condition_placeholder_2, :db_condition_placeholder_3,:db_condition_placeholder_4)) AND (ml.link_path IN (:db_condition_placeholder_5)) AND (ml.language IN (:db_condition_placeholder_6, :db_condition_placeholder_7));
Array (
  [:db_condition_placeholder_0] => 1cf698d64d1aa4b83907cf6ed55db3a7f8e92c91
  [:db_condition_placeholder_1] => navigation
  [:db_condition_placeholder_2] => management
  [:db_condition_placeholder_3] => user-menu
  [:db_condition_placeholder_4] => main-menu
  [:db_condition_placeholder_5] => node
  [:db_condition_placeholder_6] => und
  [:db_condition_placeholder_7] => ja
)

in i18n_menu_init() (line 829 of sites/all/modules/i18n/i18n_menu/i18n_menu.module).