I too have encountered this same problem and according to a search on Google a number (actually several hundred) have too.
I encountered the problem when going through some posts to update some images that were inserted. I moved all of the images that I have used in various posts into a different folder and wanted to go through my blog to update the source of each image.
After providing the correct source for the image (using the WYSIWYG wordpress editor) and clicking on SAVE, my page shows the following error:
WordPress database error: [Incorrect key file for table 'wp_posts'; try to repair it]
UPDATE IGNORE wp_posts SET post_author = '1', post_date = '2006-05-18 15:33:06', post_date_gmt = '2006-05-18 19:33:06',
Warning: Cannot modify header information - headers already sent by (output started at /home/hickory/public_html/blog/wp-includes/wp-db.php:102) in /home/hickory/public_html/blog/wp-admin/post.php on line 127
Can someone please advise how I can rectify this issue without loosing all of my posts & content. I do not have a backup of mysql database and I do have access to PHPMYADMIN for mysql. My host runs the latest version of CPANEL.