WP_options crashed

No more access to my site both for visitor and Google-robots.
Wp-admin says DB needs repair insert … so did I and click for repair.
No answer, blank page.
PHPMyAdmin demonstrate wp_options table is marked as crashed, automatique repair failed, Flush doesn’t any better.
What could be the reason for wp-options to crash?
I tried to reload wp-option table from a saved one (july 2013 which means WP V??). Still blank page for visitor or admin.
What do you sugest?
Is it a question of the structure of wp-options which has changed?

Thanks in advance.