Problems with hibernate and collections

Hello guys!

We are migrating from:
Jboss 5.0 to Jboss 6.3
java 6 to java 7
ojdbc6_g-11.2.0.2.0.jar to ojdbc7_g-12.1.0.1.jar

In Jboss 6.3 we are getting this error:

Caused by: java.lang.RuntimeException: org.hibernate.exception.GenericJDBCException: could not initialize a collection: [com.company.AClass.bs#23]

I have also tried to use ojdbc6_g-11.2.0.2.0.jar, but we get the same error.
The strange thing is that this worked fine in Jboss 5.0 and I thought that it should work as fine in Jboss 6.3.
Below is some code snippets and the db-tables (with values) that are involved.
Do you guys got any idea what might is wrong?
Best regards
Fredrik


@Entity
@Table(name = "ACLASS")
public class AClass

    @Id
    @Column(name = "ID")
    private String    id;

    @Column(name = "NAME")
    private String    name;
   
    @JoinColumn(name = "FK_ACLASS_ID")
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private Set<BClass>    bs;
   
    ...


@Entity
@Table(name = "BCLASS")
public class BClass {

    @Id
    @Column(name = "ID")
    String    id;

    @Column(name = "TYPE")
    Type    type;
   
    ...
   

public enum Type {

    A("a", "A"),
    B("b", "B"),
    C("c", "C"),
    D("d", "D"),
    E("e", "E"),
    F("f", "F");
   
    ...
   

The database tables

ACLASS
(AClass.java)

id VARCHAR2(32)
name VARCHAR2(64)

VALUES
1 name_1
2 name_2
3 name_3
4 name_4
5 name_5
6 name_6
7 name_7
8 name_8
9 name_9
10 name_10
11 name_11
12 name_12
13 name_13
14 name_14
15 name_15
16 name_16
17 name_17
18 name_18
19 name_19
20 name_20
21 name_21
22 name_22
23 name_23
24 name_24
25 name_25

   
BCLASS   
(BClass.java)

id VARCHAR2(32)
type VARCHAR2(1)
fk_aclass_id VARCHAR2(32)

VALUES
23a A 23
23b B 23
23c C 23
23e D 23
1  A 7
2  B 7
3  C 7
4  D 7
6  E 7
7  F 7
5  D 14