Back-office event registration with price set fails with fatal error - Database Error Code: Duplicate entry 'civicrm_participant-53-22-10' for key 'UI_line_item_value'

Saving a back-office event registration () for an event that has a non-quick-config price set with > 1 price field throws a fatal error:
Database Error Code: Duplicate entry 'civicrm_participant-53-22-10' for key 'UI_line_item_value', 1062

Backtrace below, but looks like it's trying to write the first line_item to the DB twice. I've attached a screenshot of the form inputs. When I look at the DB, the first of the two expected line_item rows has been inserted, and the query that fails is trying to insert the same values again.

INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , label , qty , unit_price , line_total , participant_count , price_field_value_id , financial_type_id ) VALUES ('civicrm_participant' , 53 , 10 , 'Regular Fee' , 1 , 150 , 150 , 0 , 22 , 1 ) [nativecode=1062 ** Duplicate entry 'civicrm_participant-53-22-10' for key 'UI_line_item_value']

NOTE: This is the same price set i've been using for the accounting batch export and the bookkeeping report bugs. Two price fields with price values having different Financial Types.

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/Users/dgg/svn/crm_v4.3/CRM/Core/Error.php(148): CRM_Core_Error::backtrace()
#1 [internal function](): CRM_Core_Error::handle(Object(DB_Error))
#2 /Users/dgg/svn/crm_v4.3/packages/PEAR.php(931): call_user_func((Array:2), Object(DB_Error))
#3 /Users/dgg/svn/crm_v4.3/packages/DB.php(969): PEAR_Error->PEAR_Error("DB Error: already exists", -5, 16, (Array:2), "INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...")
#4 /Users/dgg/svn/crm_v4.3/packages/PEAR.php(564): DB_Error->DB_Error(-5, 16, (Array:2), "INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...")
#5 /Users/dgg/svn/crm_v4.3/packages/DB/common.php(1905): PEAR->raiseError(NULL, -5, NULL, NULL, "INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...", "DB_Error", TRUE)
#6 /Users/dgg/svn/crm_v4.3/packages/DB/mysql.php(898): DB_common->raiseError(-5, NULL, NULL, NULL, "1062 ** Duplicate entry 'civicrm_participant-53-22-10' for key 'UI_line_item_...")
#7 /Users/dgg/svn/crm_v4.3/packages/DB/mysql.php(327): DB_mysql->mysqlRaiseError()
#8 /Users/dgg/svn/crm_v4.3/packages/DB/common.php(1216): DB_mysql->simpleQuery("INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...")
#9 /Users/dgg/svn/crm_v4.3/packages/DB/DataObject.php(2421): DB_common->query("INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...")
#10 /Users/dgg/svn/crm_v4.3/packages/DB/DataObject.php(1055): DB_DataObject->_query("INSERT INTO civicrm_line_item (entity_table , entity_id , price_field_id , la...")
#11 /Users/dgg/svn/crm_v4.3/CRM/Core/DAO.php(287): DB_DataObject->insert()
#12 /Users/dgg/svn/crm_v4.3/CRM/Price/BAO/LineItem.php(65): CRM_Core_DAO->save()
#13 /Users/dgg/svn/crm_v4.3/CRM/Price/BAO/LineItem.php(291): CRM_Price_BAO_LineItem::create((Array:17))
#14 /Users/dgg/svn/crm_v4.3/CRM/Event/Form/Participant.php(1491): CRM_Price_BAO_LineItem::processPriceSet(53, (Array:2), Object(CRM_Contribute_BAO_Contribution), "civicrm_participant")
#15 /Users/dgg/svn/crm_v4.3/CRM/Core/Form.php(246): CRM_Event_Form_Participant->postProcess()
#16 /Users/dgg/svn/crm_v4.3/CRM/Core/QuickForm/Action/Upload.php(151): CRM_Core_Form->mainProcess()
#17 /Users/dgg/svn/crm_v4.3/CRM/Core/QuickForm/Action/Upload.php(128): CRM_Core_QuickForm_Action_Upload->realPerform(Object(CRM_Event_Form_Participant), "upload")
#18 /Users/dgg/svn/crm_v4.3/packages/HTML/QuickForm/Controller.php(203): CRM_Core_QuickForm_Action_Upload->perform(Object(CRM_Event_Form_Participant), "upload")
#19 /Users/dgg/svn/crm_v4.3/packages/HTML/QuickForm/Page.php(103): HTML_QuickForm_Controller->handle(Object(CRM_Event_Form_Participant), "upload")
#20 /Users/dgg/svn/crm_v4.3/CRM/Core/Controller.php(316): HTML_QuickForm_Page->handle("upload")
#21 /Users/dgg/svn/crm_v4.3/CRM/Event/Page/Tab.php(115): CRM_Core_Controller->run()
#22 /Users/dgg/svn/crm_v4.3/CRM/Event/Page/Tab.php(183): CRM_Event_Page_Tab->edit()
#23 /Users/dgg/svn/crm_v4.3/CRM/Core/Invoke.php(292): CRM_Event_Page_Tab->run((Array:4), NULL)
#24 /Users/dgg/svn/crm_v4.3/CRM/Core/Invoke.php(70): CRM_Core_Invoke::runItem((Array:12))
#25 /Users/dgg/svn/crm_v4.3/CRM/Core/Invoke.php(52): CRM_Core_Invoke::_invoke((Array:4))
#26 /Users/dgg/svn/crm_v4.3/drupal/civicrm.module(407): CRM_Core_Invoke::invoke((Array:4))
#27 [internal function](): civicrm_invoke("contact", "view", "participant")
#28 /Users/dgg/htdocs/drupal7/includes/menu.inc(516): call_user_func_array("civicrm_invoke", (Array:3))
#29 /Users/dgg/htdocs/drupal7/index.php(21): menu_execute_active_handler()
#30

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