Problems creating a trigger in Oracle 11g

I get a weird error while trying to create a trigger in my Oracle 11g database using SQL Developer. Here is what I did:

My table:

CREATE TABLE COUNTRY_CODE(
   ID NUMBER(19,0)      PRIMARY KEY NOT NULL, 
   Code             VARCHAR2(2) NOT NULL,
   Description  VARCHAR2(50),
   created                  TIMESTAMP DEFAULT CURRENT_TIMESTAMP, 
   created_by                   VARCHAR2(40) DEFAULT USER, 
   last_updated                 TIMESTAMP DEFAULT CURRENT_TIMESTAMP, 
   last_updated_by          VARCHAR2(40) DEFAULT USER,
   archived CHAR(1) DEFAULT '0' NOT NULL );

The Sequence:

CREATE SEQUENCE COUNTRY_CODE_ID_SEQ START WITH 1 INCREMENT BY 1;

The trigger:

CREATE OR REPLACE TRIGGER COUNTRY_CODE_TRIGGER
BEFORE INSERT ON COUNTRY_CODE
FOR EACH ROW
DECLARE
    max_id number;
    cur_seq number;
BEGIN
    IF :new.id IS NULL THEN
    SELECT COUNTRY_CODE_ID_SEQ.nextval
    INTO :new.id
    FROM dual;
ELSE
    SELECT GREATEST(NVL(MAX(id),0), :new.id)
    INTO max_id
    FROM COUNTRY_CODE;

    SELECT COUNTRY_CODE_ID_SEQ.nextval
    INTO cur_seq
    FROM dual;

    WHILE cur_seq < max_id
    LOOP
        SELECT COUNTRY_CODE_ID_SEQ.nextval
        INTO cur_seq
        FROM dual;
    END LOOP;
END IF;
END;

Creating the table and the sequence works very well, but when I try to create my trigger, I get this error:

Error report:
ORA-00603: ORACLE server session terminated by fatal error
ORA-00600: internal error code, arguments: [kqlidchg0], [], [], [], [], [], [], [], [], [], [], []
ORA-00604: error occurred at recursive SQL level 1
ORA-00001: unique constraint (SYS.I_PLSCOPE_SIG_IDENTIFIER$) violated
00603. 00000 -  "ORACLE server session terminated by fatal error"
*Cause:    An ORACLE server session is in an unrecoverable state.
*Action:   Login to ORACLE again so a new server session will be created

Does anyone know about this error?

Thanks