try:

INSERT INTO zen_configuration (configuration_title, configuration_key, configuration_value, configuration_description, configuration_group_id, sort_order, set_function, date_added) VALUES ('Cross-Sell - Display prices?', 'XSELL_DISPLAY_PRICE', 'false', 'Cross-Sell -- Do you want to display the product prices too?
Default: false', 18, 72, 'zen_cfg_select_option(array(true,false), ', now());