plpy prepare problem

["jlowery" <jslowery@xxxxxxxxx>]

I'm having a bit of a problem getting plpython's prepare to work
properly:

CREATE OR REPLACE FUNCTION batch_item_reversal(b batch_item)
  RETURNS "varchar" AS
$BODY$

if b['reversal_flag'] == 'Y':
	sql = plpy.prepare("""
		SELECT batch_item_number
		FROM batch_item
		WHERE patient_ssn=$1 AND
			patient_dob=$1 AND
			claim_number=$1 AND
			batch_item_number != $1""",
		["varchar", "date", "varchar", "varchar"])
	refs = plpy.execute(sql, [
		b['patient_ssn'],
		b['patient_dob'],
		b['claim_number'],
		b['batch_item_number']])

	refs2 = plpy.execute("""
		SELECT batch_item_number
		FROM batch_item
		WHERE patient_ssn='%s' AND
			patient_dob='%s' AND
			claim_number='%s' AND
			batch_item_number != '%s'
		""" % (b['patient_ssn'],
		       b['patient_dob'],
                       b['claim_number'],
                       b['batch_item_number']))

	if refs:
		return refs[0]["batch_item_number"]
	else:
		return "ERROR"
else:
	return None

$BODY$
  LANGUAGE 'plpythonu' VOLATILE;


Here, refs2 returns the proper data, but refs always returns nothing.
I have a feeling it has something to do with the type list, I tried
all "text"'s but to no avail.