Undefined index: footer in /includes/common.inc on line 2291.

ahah_helper makes Drupal throw countless of errors, because of:

  drupal_add_js(drupal_get_path('module', 'ahah_helper') .'/ahah_helper.js', 'footer');

The intention was $scope, but $module comes before. See drupal_add_js().

This bug applies to all versions of ahah_helper. hook_init() in 1.x, some helper function in 2.x.

This also means it was never loaded in the footer as intended. Instead, it's loaded in the header, as Drupal core defaults to that for all unknown scopes.