Well..i tried to do exactly what you said...

+++++++++++++++++++++++++++++++++++++++++++++++++
SQL> insert into mydate values to_date('7/1/1998', 'DD-MON-YYYY');
insert into mydate values to_date('7/1/1998', 'DD-MON-YYYY')
*
ERROR at line 1:
ORA-03001: unimplemented feature


SQL> show parameter nls_

NAME TYPE VALUE
------------------------------------ ----------- --------------------
nls_calendar string
nls_comp string
nls_currency string
nls_date_format string
nls_date_language string
nls_dual_currency string
nls_iso_currency string
nls_language string AMERICAN
nls_length_semantics string BYTE
nls_nchar_conv_excp string FALSE
nls_numeric_characters string
nls_sort string
nls_territory string AMERICA
nls_time_format string
nls_time_tz_format string
nls_timestamp_format string
nls_timestamp_tz_format string

+++++++++++++++++++++++++++++++++++++++

any suggestions ?..

Thanks
Ron