Severe Database Corruption.

I’m trying to help a friend through this one, but it’s stumping me.

He’s got a pretty large wordpress install -> 46,000 posts, 120,000 comments, 12,000 subscribers, 20 cateogies, no tags. The database itself is 450MB at the moment.

About a week ago, he tried to optimise the database using cpanel. The command failed or stalled, and he had to restart the server to get it back online. On the front-end, everything is working fine and no errors are encountered. On the backend, these things happen:

– ALL Categories, Comments, Users, and Posts disappear and reappear randomly! This doesnt happen simultaneously. On Dashboard for example, you might see how many comments, but no posts. If you go to edit-comments.php, you see no comments but when you refresh the page they appear. The most annoying effect is probably when Writing Posts, and the categories don’t appear.

– The WordPress “Database Upgrade” notice appears like twice per day when visiting the wp-admin pages. No upgrades is necessary he’s already running 2.7. Of course, clicking Upgrade does nothing. Only way to get rid of this is to restart mysql.

I have tried repairing and optimising mysql via Cpanel and from ssh with ‘mysqlcheck’ and ‘myisamchk’ with no success.

Any suggestions please ?