ERROR: array value must start with "{" or dimension information

I am trying to INSERT a record in my postgres table and I get t his error:
ERROR:  array value must start with "{" or dimension information

My table definnition
CREATE TABLE paymentmethod
(
  code varchar(1) NOT NULL,
  description varchar(30)[] NOT NULL
)
WITH OIDS;
ALTER TABLE paymentmethod OWNER TO postgres;
GRANT ALL ON TABLE paymentmethod TO postgres;
COMMENT ON TABLE paymentmethod IS 'Payment Method Table';

My Insert SQL:

insert into paymentmethod
values('A','ACH');

Do you know what might be causing the problem?