Error: 1017

Hi, I had a problem with my wiki homepage reports this error:

A database error has occurred
Query: SELECT
user_name,user_password,user_newpassword,user_emai l,user_email_authenticated,user_real
_name,user_options,user_touched,user_token FROM `user` WHERE user_id =
'1' LIMIT 1
Function: User::loadFromDatabase
Error: 1017 Can't find file: 'user.MYI' (errno: 2) (localhost)

Backtrace:

* GlobalFunctions.php line 450 calls wfbacktrace()
* Database.php line 397 calls wfdebugdiebacktrace()
* Database.php line 347 calls databasemysql::reportqueryerror()
* Database.php line 723 calls databasemysql::query()
* Database.php line 742 calls databasemysql::select()
* User.php line 679 calls databasemysql::selectrow()
* User.php line 625 calls user::loadfromdatabase()
* Setup.php line 216 calls user::loadfromsession()
* index.php line 63 calls require_once()

Can you help me?
Tahnks in advance.