I had a weird WordPress 3.0 issue in one of our sites after doing an auto-upgrade.
- create a new post
- edit an existing post
- open up the collapsible menu in the side in admin
- quick edit posts
None of it worked. After browsing the WordPress.org forums, I came across a tip pointing to a particular db.php file in wp-contents folder. Renaming that file to db.php.0 worked!
- Go to wp-content
- Backup and delete db.php file if you have one.
It appears that plugins like DB Cache, DB Caching Reloaded, etc create this file which leads to unresponsive WordPress admin area. Hopefully, this will help some of you facing the same issue.