Line 945 in sociable.php, the wrong meta_key name is used:
$wpdb->query("DELETE FROM $wpdb->postmeta WHERE meta_key = 'sociableoff'");
should be
$wpdb->query("DELETE FROM $wpdb->postmeta WHERE meta_key = '_sociableoff'");
I also can't seem (or could not) to get 4 posts that had this meta_key set to turn it off in wp_postmeta table; I would edit the post and this value was checked in the UI - I'd uncheck it, Update post and it would not remove that value from the underlying DB. Digging into my DB and your code let me delete them by hand and now it's all fine, but something's not right in there...
WP 2.8.6 and Sociable 3.5.2 on CentOS5.