Problems using FOREIGN KEYs

After defining the following database tables everthing works fine.

CREATE TABLE TestBenutzer

      (BN_ID                    NUMBER(15) NOT NULL,
       GR_ID                    NUMBER(15) NULL,
       BN_Name                  VARCHAR2(30) NOT NULL,
       BN_Vorname               VARCHAR2(30) NULL,
       BN_Abtbezeichnung        VARCHAR2(30) NULL

CREATE UNIQUE INDEX XPKTestBenutzer
  ON TestBenutzer
(

BN_ID                            ASC

CREATE TABLE Gruppe

      (GR_ID                    NUMBER(15) NOT NULL,
       GR_Name_kurz             VARCHAR2(30) NOT NULL,
       GR_Beschreibung          VARCHAR2(80) NULL

CREATE UNIQUE INDEX XPKGruppe
  ON Gruppe
(

GR_ID                            ASC

ALTER TABLE TestBenutzer
ADD ( PRIMARY KEY (BN_ID) )
;

ALTER TABLE Gruppe
ADD ( PRIMARY KEY (GR_ID) )
;

But after altering the table "TestBenutzer"

ALTER TABLE TestBenutzer
ADD ( FOREIGN KEY (GR_ID)
               REFERENCES Gruppe)
;

the message

Message: ORA-00600:internal error code, arguments:[12832],[],[],[],[],[],[],[]

is displayed if you try to insert a new row into the table "TestBenutzer".

The Oracle 7 manual "Messages and Codes" advices to report this problem to "World Wide Customer Support", because it is an internal exception, but we believe there is an mistake in our definition.

We are using Oracle 7 running on a NetWare 3.11-Server.

Is anybody able to help us?

Ciao
Dirk Fleischmann and Frank Wolf

---
Dirk Fleischmann        Hochschulrechenzentrum, TH Darmstadt
Petersenstrasse 30                          __o    
64287 Darmstadt                           _`\<,_   
Germany                                  (_)/ (_)
E-Mail (Internet): fleischmann_at_hrz.th-darmstadt.de