Getting a null pointer exception while commiting

I'm trying to instanciate the model (see attachment) and when I commit
the surrounding Read/Write transaction, I get the following exception:

org.netbeans.mdr.persistence.StorageTransientDataException:
java.lang.NullPointerException: null
        at
org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeDatabase.writeS
treamable(BtreeDatabase.java:877)
        at
org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeDatabase.addRec
ord(BtreeDatabase.java:916)
        at
org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeDatabase.save(B
treeDatabase.java:502)
        at
org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeDatabase.commit
Changes(BtreeDatabase.java:418)
        at
org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeStorage.commitC
hanges(BtreeStorage.java:313)
        at
org.netbeans.mdr.storagemodel.MdrStorage.save(MdrStorage.java:532)
        at
org.netbeans.mdr.storagemodel.MdrStorage.commit(MdrStorage.java:503)
        at
org.netbeans.mdr.util.TransactionMutex.leave(TransactionMutex.java:183)
        at
org.netbeans.mdr.NBMDRepositoryImpl.endTrans(NBMDRepositoryImpl.java:202
)
        ...



When importing my model, I perform some checks to ensure the model can
be correctly instantiated.

Before committing, I dont't have any problem creating  a new extent. I
can see a valid MOF ID for my nex extent. But as soon as I commit, this
exception is raised and, of course, when I try to find the extent, a
null reference is returned, indicating no such extent exist.

Nevertheless, this may be linked to my model because I can correctly
instanciate another model. But I don't understand.

The MDR build number is : 200307311024 (MDR Standalone).
 
Thanks for your help.

Regards.

Olivier.