Error when saving individual form settings

When I try to change the "Text analysis accuracy" on a specific form (admin/config/content/mollom/manage/webform_client_form_17) to a different setting and click save, sometimes it saves just fine, sometimes it throws an error:
The website encountered an unexpected error. Please try again later.

And this shows up in dblog:

PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'entity' in 'field list':
UPDATE {mollom_form} SET
entity = :db_update_placeholder_0,
bundle = :db_update_placeholder_1,
mode =   :db_update_placeholder_2,
checks = :db_update_placeholder_3,
unsure = :db_update_placeholder_4,
discard = :db_update_placeholder_5,
moderation = :db_update_placeholder_6,
enabled_fields = :db_update_placeholder_7,
strictness = :db_update_placeholder_8,
module = :db_update_placeholder_9
WHERE (
  form_id = :db_condition_placeholder_0
);

Array (
[:db_update_placeholder_0] => webform
[:db_update_placeholder_1] => 
[:db_update_placeholder_2] => 2 
[:db_update_placeholder_3] => a:2:{i:0;s:4:"spam";i:1;s:9:"profanity";} 
[:db_update_placeholder_4] => captcha 
[:db_update_placeholder_5] => 1 
[:db_update_placeholder_6] => 0 
[:db_update_placeholder_7] => a:9:{i:0;s:15:"submitted][name";i:1;s:24:"submitted][email_address";i:2;s:23:"submitted][phone_number";i:3;s:32:"submitted][street_address_line_1";i:4;s:32:"submitted][street_address_line_2";i:5;s:15:"submitted][city";i:6;s:36:"submitted][state___province___region";i:7;s:28:"submitted][zip___postal_code";i:8;s:18:"submitted][message";}
[:db_update_placeholder_8] => relaxed
[:db_update_placeholder_9] => webform
[:db_condition_placeholder_0] => webform_client_form_17
)
in drupal_write_record() (line 7106 of /mnt/www/hcl/includes/common.inc).

It happens with multiple forms, not just one.