If, when trying to add a custom field to a post, you get the following message:
“Please provide a custom field value”
This message is misleading. It’s the AJAX javacript generated error message which is not customized for database errors.
So potentially you have a bit of a nasty problem: database corruption.
You may now notice some other problems with your wordpress like missing thumbnails in your media library. It’s ugly.
BUT THERE IS A FIX!
1. Go to your website cpanel and run phpMyAdmin
2. Open your wordpress database
3. Find the table wp_postmeta – if you have set your table up with a prefix, adjust the instructions below accordingly
At this point if you find a warning message saying it has crashed, you are in luck. Otherwise, you need to surf for another solution…
4. Open the SQL tab for wp_postmeta table
5. type REPAIR TABLE wp_postmeta and hit Go
That should be it. Other crashed tables can be repaired in the same way.