trying to edit post, got error

[loveley]

While trying to edit post in my forum, I got this error:

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
126 - Incorrect key file for table './xxx/xxx_posts.MYI'; try to repair it
Query:
UPDATE nnz_posts SET `subject`='Aizņemtās sejas', `message`='...', `icon`='0', `smilieoff`='0', `includesig`='1', `visible`='1' WHERE pid='23'

Could someone help me to understand this error and how to fix it?

Happens to all users, not only me. :/

Solved the problem by repairing table threads.