corrupted mos_session table

 10 minutes ago, I got a strange error message:

DB function failed with error number 1016
Can’t open file: ‘mos_session.MYI’. (errno: 145) SQL=SELECT session_id FROM mos_session WHERE session_id=MD5(‘e20eafcf277b7bc0dd125357b4a1b223’)
SQL =
SELECT session_id FROM mos_session WHERE session_id=MD5(‘e20eafcf277b7bc0dd125357b4a1b223’

I was not able to access the frontend or admin panel of my homepage. I tried to look in PHPMyAdmin the table mos_session but was getting the same error message. The only solution was to recreate the table with the following code:

DROP TABLE IF EXISTS `mos_session`;
CREATE TABLE `mos_session` (
  `username` varchar(50) default '',
  `time` varchar(14) default '',
  `session_id` varchar(200) NOT NULL default '0',
  `guest` tinyint(4) default '1',
  `userid` int(11) default '0',
  `usertype` varchar(50) default '',
  `gid` tinyint(3) unsigned NOT NULL default '0',
  PRIMARY KEY  (`session_id`),
  KEY `whosonline` (`guest`,`usertype`)
) TYPE=MyISAM;

Why my table has crashed is still unknow but I am looking further in logs files…