'You may not submit another entry at this time.'on Drupal 7.8

It is impossible to fill out forms after upgrading from 7.x-3.13 to 7.x-3.18 due to maximum submission limits.

Upgrades executed by drupal:

• 7317 - Add an index for 'nid_sid' to webform_submissions.
• 7318 - Upgrade file components to support the new AJAX-upload element.
• 7319 - Add file usage entries for all files uploaded through Webform.
• 7320 - Mark files uploaded through Webform that report active usage permanent.

Result:

• This PHP notice is displayed after the update but this is most likely unrelated:
  Notice: Undefined variable: output in ctools_var_export() (line 837 of /sites/all/modules/contrib/ctools/includes/export.inc).
• When trying to fill out a form, the message from the subject of this issue is displayed
• When trying to correct the submission limit to fix the problem using node/[nid]/webform/configure and setting the TOTAL SUBMISSIONS LIMIT to 'unlimited' (as it is set to an emtpty limit by default) a PHP notices are displayed and a PDO exception is thrown:
  

  Notice: Undefined index: total_submit_limit in webform_configure_form() (line 96 of /sites/all/modules/contrib/webform/includes/webform.pages.inc).
  Notice: Undefined index: total_submit_limit in webform_configure_form() (line 103 of /sites/all/modules/contrib/webform/includes/webform.pages.inc).
  Notice: Undefined index: total_submit_limit in webform_configure_form() (line 103 of /sites/all/modules/contrib/webform/includes/webform.pages.inc).
  Notice: Undefined index: total_submit_interval in webform_configure_form() (line 114 of /sites/all/modules/contrib/webform/includes/webform.pages.inc).
  PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'total_submit_limit' in 'field list': UPDATE {webform} SET confirmation=:db_update_placeholder_0, confirmation_format=:db_update_placeholder_1, redirect_url=:db_update_placeholder_2, status=:db_update_placeholder_3, block=:db_update_placeholder_4, teaser=:db_update_placeholder_5, allow_draft=:db_update_placeholder_6, auto_save=:db_update_placeholder_7, submit_notice=:db_update_placeholder_8, submit_text=:db_update_placeholder_9, submit_limit=:db_update_placeholder_10, submit_interval=:db_update_placeholder_11, total_submit_limit=:db_update_placeholder_12, total_submit_interval=:db_update_placeholder_13 WHERE (nid = :db_condition_placeholder_0) ; Array ( [:db_update_placeholder_0] => [:db_update_placeholder_1] => page_content [:db_update_placeholder_2] => <confirmation> [:db_update_placeholder_3] => 1 [:db_update_placeholder_4] => 0 [:db_update_placeholder_5] => 0 [:db_update_placeholder_6] => 0 [:db_update_placeholder_7] => 0 [:db_update_placeholder_8] => 1 [:db_update_placeholder_9] => [:db_update_placeholder_10] => -1 [:db_update_placeholder_11] => -1 [:db_update_placeholder_12] => -1 [:db_update_placeholder_13] => -1 [:db_condition_placeholder_0] => 53 ) in drupal_write_record() (line 6868 of /includes/common.inc).

• webform_update_7316() does somehow not get executed properly since the two new columns in there are not added to the webform table!

Solution to fix your immediate problem if you have this case, is executing these SQL queries:

alter table webform add column total_submit_limit int default -1;
alter table webform add column total_submit_interval int default -1;

Solution to fix the module:
To be determined