Custom fields not being stored in database

Hi all,

Since yesterday all of a sudden my custom fields are no longer being saved in the database. I never had this problem before and nothing has changed on the server or with the WordPress installation. I’m using a custom field in my template for the main image of the post to display on the homepage. When I add this field I don’t see it being added to the wp_postmeta table in the database. For the latest post I inserted it manually to the database, which works but of course is no long term solution.

How can this all of a sudden stop working after running the site for over a year? And more importantly, how can I fix this?

Just to be clear; the custom field in question doesn’t start with an underscore (_), so it won’t be seen as a protected field by WP.

Any ideas?

Cheers,
Ruben.