Post metadata deletes itself

I’m using a custom post type for a portfolio. I have a few option in there, bring saved by update_post_meta(), it seems to work fine, but then out of the blue (within the hour), the data deletes its self. I have looked in the DB and all custom metadata values are empty.

I’m a little stumped really.

Here’s the code that’s saving one of the options.

function update_colour_palette(){
    global $post;
    $color = get_post_custom($post->ID);
 $palette = $color["palette"][0];
    update_post_meta($post->ID, "palette", $_POST["palette"], $palette);
}

Any help, tips & tricks would be useful.

I’ve been using this for a while to solve exactly your issue, I think I got it from the codex somewhere. But it works.

// verify if this is an auto save routine. 
// If it is our form has not been submitted, so we dont want to do anything
    if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE )
        return $post_id;