ora-604 when trigger runs

OS:win XP sp3

DB:10.2.0.1

purpose:

i want to prevent cretical IP address from login database.

my scripts:

TABLE:

CREATE TABLE "SYSTEM"."USER_LOGIN_LOG1"
  ( "LOGIN_DATE" DATE,
 "USERNAME" VARCHAR2(100),
 "LOGIN_IP" VARCHAR2(100),
 "MACHINE" VARCHAR2(100),
 "PROGRAM" VARCHAR2(100)
   ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS NOLOGGING
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
TABLESPACE "USERS";

TRIGGER :

CREATE OR REPLACE TRIGGER TRI_LOGON_DMM_DB
AFTER LOGON
ON DATABASE
declare
  v_program  VARCHAR2(100);
  v_ip       VARCHAR2(20);
  v_machine  VARCHAR2(100);
  v_len      number(10);
  v_username varchar2(100);
  v_sid      number;
  v_serial   number;
  v_sql      varchar2(100);
begin
   SELECT a.PROGRAM,
         nvl(SYS_CONTEXT('USERENV', 'IP_ADDRESS'), 'aaa'),