Function problem -- how do I drop this function?

I have created the following procedure (using phpPgAdmin -- which is very
buggy).  When I try to drop it using 'drop function CreateUser();', I am
told it does not exist.  If I try using 'drop function
CreateUser(varchar(12), varchar(12), varchar(30), char(1), varchar(30),
varchar(30), boolean)', I am told it does not exist either.  If I try it
from phpPgAdmin, I get this error;

"PostgreSQL said: ERROR: parser: parse error at or near "varying"
Your query:
DROP FUNCTION
"CreateUser"(character,varying,,character,varying,,character,varying,,charac
ter,,character,varying,,character,varying,,boolean)
".

So, is there no way to drop this function?

CREATE FUNCTION CreateUser(varchar(12), varchar(12), varchar(30), char(1),
varchar(30), varchar(30), boolean) RETURNS int4 AS '
DECLARE
    id int4;
    un ALIAS FOR $1;
    pw ALIAS FOR $2;
    fn ALIAS FOR $3;
    mi ALIAS FOR $4;
    ln ALIAS FOR $5;
    ea ALIAS FOR $6;
    a  ALIAS FOR $7;
BEGIN
    SELECT id = nextval('users_id_seq');
    INSERT INTO users (id, username, password, firstname, middleinitial,
lastname, emailaddr, admin)
    VALUES (id, un, pw, fn, mi, ln, ea, ad);
    RETURN id;
END  ' LANGUAGE 'plpgsql';

Thanks,

Tom Veldhouse
veldy@veldy.net