PDOException: SQLSTATE[42000]

[admin.1]

Hi!
My site (http://ssl3.co.cc) was working fine untill this morning (~12hrs). I did not do any mysql editing. And I logged out of every page successfully.
Now from out of the blue the site is showing error messages. Please solve this problem
I'm using drupal.

The message is:

Error
The website encountered an unexpected error. Please try again later.

PDOException: SQLSTATE[42000]: Syntax error or access violation: 1286 Unknown table engine 'InnoDB': SELECT expire, value FROM {semaphore} WHERE name = :name; Array ( [:name] => variable_init ) in lock_may_be_available() (line 167 of /home/nix/public_html/includes/lock.inc).

Uncaught exception thrown in shutdown function.

PDOException: SQLSTATE[42000]: Syntax error or access violation: 1286 Unknown table engine 'InnoDB': DELETE FROM {semaphore} WHERE (value = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] => 16631890634e75f959ce95d1.50250785 ) in lock_release_all() (line 269 of /home/nix/public_html/includes/lock.inc).