can't set sequence

Hi All,

In our database we have a table as described below.  When we attempt to write
to the table from our visual basic program we receive an error.  "ERROR:
tbl_receiving_receipt_number_seq.nextval:  You don't have permissions to set
sequence tbl_receiving_receipt_number_seq"  Can someone please explain how to
correct this error?  TIA

-- Table: purchase_order.tbl_receiving

-- DROP TABLE purchase_order.tbl_receiving;

CREATE TABLE purchase_order.tbl_receiving
(
  po_number int4 NOT NULL,
  po_line int2 NOT NULL,
  receipt_number serial NOT NULL,
  quantity float4 NOT NULL,
  receipt_timestamp timestamp NOT NULL DEFAULT ('now'::text)::timestamp(6)
with time zone,
  CONSTRAINT tbl_receiving_pkey PRIMARY KEY (po_number, po_line, receipt_number),
  CONSTRAINT tbl_receiving_fkey1 FOREIGN KEY (po_number, po_line) REFERENCES
purchase_order.tbl_line_item (po_number, po_line) ON UPDATE CASCADE ON DELETE
RESTRICT
) WITH OIDS;
GRANT ALL ON TABLE purchase_order.tbl_receiving TO public;
GRANT ALL ON TABLE purchase_order.tbl_receiving TO postgres;
GRANT UPDATE, INSERT ON TABLE purchase_order.tbl_receiving TO GROUP loaders;
COMMENT ON TABLE purchase_order.tbl_receiving IS 'Purchase order item
receiving data.';

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