For v1.3.8, you would open phpMyAdmin, choose your database from the pulldown menu on the left, then click the "SQL" tab on the right, and paste this into the command window, and click Go:
Code:
DROP TABLE IF EXISTS sessions;
CREATE TABLE sessions (
sesskey varchar(32) NOT NULL default '',
expiry int(11) unsigned NOT NULL default '0',
value mediumblob NOT NULL,
PRIMARY KEY (sesskey)
) TYPE=MyISAM;
You should be reporting this database problem to your hosting company or server administrator ... because database corruption such as you're talking about shouldn't be happening.