I recently had a problem trying to use mysqldump where it was complaining that
mysqldump: Got error: 145: Table './recurser/wp_options' is marked as crashed and should be repaired when using LOCK TABLES
This corrupted wp_options table actually caused wordpress to think it was a fresh install, and showed the interface to create the admin user to anyone who accessed recurser which is a little scary :)
The solution was to go to the actual database directory, and run myisamchk -r on the offending table :
> cd /var/lib/mysql/recurser > myisamchk -r wp_options (06-18 19:16) - recovering (with sort) MyISAM-table 'wp_options' Data records: 181 - Fixing index 1 - Fixing index 2
After this everything seemed to run normally again. There are a lot of other myisamchk options if this simple fix doesn’t work for you - if the man pages aren’t any help a quick google should reveal loads of info.