Database Repair & WP-DBManager

Hi,
I installed WP-DBManager plugin and performed an optimize function in an effort to improve performance of my site.
This caused WordPress to run into database errors, and suggested I perform a database repair, which I’ve done.
However I’m now returned the following errors:

wp_usermeta: Table is marked as crashed and last repair failed
wp_posts: Table is marked as crashed and last repair failed
wp_comments: Table is marked as crashed and last repair failed
wp_options: Table is marked as crashed and last repair failed
wp_postmeta: Table is marked as crashed and last repair failed
wp_terms: Table is marked as crashed and last repair failed
wp_term_taxonomy: Table is marked as crashed and last repair failed
wp_commentmeta: Table is marked as crashed and last repair failed

I’m really stuck! What should I do to remedy this errors>
Thanks in advance.