SQL & PL/SQL

Hi expert,

I ran a simple query as follows:

select *
FROM HIROC_RM021_CPD_DEST1
where to_date('04/01/'||substr(LOSS_YEAR,instr(LOSS_YEAR,',')+2,4),'mm/dd/yyyy') BETWEEN
to_date('4/1/2006','mm/dd/yyyy') and to_date('4/1/2010','mm/dd/yyyy')

got some error message as follows:

" ORA-01840 : input value not long enough for date format"

definition for table " FROM HIROC_RM021_CPD_DEST1" is as follows:

CREATE TABLE HIROC_RPT_USER.HIROC_RM021_CPD_DEST1
(
POLICY_START_DATE DATE,
POLICY_END_DATE DATE,
LOSS_YEAR VARCHAR2(500 BYTE),
SUBSCRIBERNAME VARCHAR2(500 BYTE),
AMAL_SUBSCRIBERNAME VARCHAR2(500 BYTE),
ORG_POLICY_NO VARCHAR2(500 BYTE),
PARENT_POLICY_NO VARCHAR2(500 BYTE),
PEER_GROUP VARCHAR2(10 BYTE),
PEER_GROUP_DESC VARCHAR2(500 BYTE),
INDEMNITY_PAYMENT NUMBER(13,2),
PAID NUMBER(13,2),
TOTAL_RESERVE NUMBER(13,2),
DELIVERIES NUMBER(13,2),
CLAIMS_COUNT NUMBER(13,2),
AMALGAMATED VARCHAR2(10 BYTE),
PROVINCE VARCHAR2(50 BYTE)
)
TABLESPACE PRODDW_DATA
PCTUSED 0
PCTFREE 10
INITRANS 1
MAXTRANS 255
STORAGE (
INITIAL 64K
NEXT 64K
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0
BUFFER_POOL DEFAULT
)
LOGGING
NOCOMPRESS
NOCACHE
NOPARALLEL
MONITORING;

will you please help me to get it resolved? appreciate very much.