SQL & PL/SQL

I am getting this error:

Error report -

SQL Error: ORA-00918: column ambiguously defined

00918. 00000 -  "column ambiguously defined"

*Cause:   

*Action:

when I use this type of SQL syntax:

[CODE]

INSERT INTO a1_security_action (object_id,

                                discriminant,

                                action_nbr,

                                description,

                                sort_order

                               )

  WITH names AS

   (SELECT 'ABCE',

           'X',

           1,

           'Open',

           1

      FROM dual

     UNION ALL

    SELECT 'ABCE','X',2,'Terms',2

      FROM dual

     UNION ALL

    SELECT 'ACAIM','X',1,'G/L Distribution',1

      FROM dual

   )

SELECT * FROM names

/

[/CODE]

info a1_security_action
produces this result:

[CODE]

Columns
NAME           DATA TYPE            NULL  DEFAULT    COMMENTS
*ACTION_NBR    NUMBER(5,0)          No    1             
*DISCRIMINANT  VARCHAR2(10 BYTE)    No    'X'           
*OBJECT_ID     VARCHAR2(10 BYTE)    No                  
DESCRIPTION   VARCHAR2(100 BYTE)   No                  
SORT_ORDER    NUMBER(5,0)          No                  
Indexes
INDEX_NAME                      UNIQUENESS  STATUS  FUNCIDX_STATUS  COLUMNS                              COLUMN_EXPRESSION 
GRAINV18.PK_A1_SECURITY_ACTION  UNIQUE      VALID                   OBJECT_ID, DISCRIMINANT, ACTION_NBR                    

References
TABLE_NAME               CONSTRAINT_NAME              DELETE_RULE  STATUS   DEFERRABLE      VALIDATED  GENERATED 
A1_SECURITY_ACTION_ROLE  FK2_A1_SECURITY_ACTION_ROLE  NO ACTION    ENABLED  NOT DEFERRABLE  VALIDATED  USER NAME

[/CODE]

Any Ideas???

Thanks