ANOTHER SOLUTION
I was exhibiting similar symptoms as listed in this thread, but on a WP 2.7.1 development site that had worked fine for a month or so. Couldn’t save or create Pages, Posts, or even Users. Like others, tried multiple browsers, disabling all plugins, cache, cookies, and even a clean WordPress install then a database import. Nothing in index.php was out of the ordinary, nor was there any reason to think an unpublished site would be hacked.
Long story short, the problem for me ended up being that the “auto_increment” attribute had disappeared from the ID field in each table of the database (!!!!). All the default WP tables except for wp_term_relationships should have auto_increment set on their ID fields. With it gone, the ID for any save defaulted to 0, causing all sorts of craziness. Adding “auto_increment” back in and deleting any rows with ID “0” that had been added in while I was trying to figure things out seems to have resolved the problem.
An SQL Query to make the appropriate changes all at once is:
ALTER TABLE wp_comments CHANGE comment_ID comment_ID BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_links CHANGE link_id link_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_options CHANGE option_id option_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_postmeta CHANGE meta_id meta_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_posts CHANGE ID ID BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_term_taxonomy CHANGE term_taxonomy_id term_taxonomy_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_terms CHANGE term_id term_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_usermeta CHANGE umeta_id umeta_id BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
ALTER TABLE wp_users CHANGE ID ID BIGINT( 20 ) UNSIGNED NOT NULL AUTO_INCREMENT;
Plugins I had active when the issue occurred:
Blogroll Page
Constant Contact Widget
FirePHP
Menubar (recently upgraded)
NextGEN Custom Fields
NextGEN Gallery
TinyMCE Advanced
Use Google Library Javascript
WP Minify
Plugins that weren’t active, but I auto-upgraded:
Mass Page Maker
Wordpress Navigation List Plugin NAVT
