Hi!
I am using JBoss 3.0.4 and found one interesting thing.
I have 2 beans: EmployeeBean and UserBean. There is a 1-to-1 UNIDIRECTIONAL relationship between them - there is CMR field (UserLocal user) in EmployeeBean.
So, ejb-jar looks like:

<ejb-relation>

<ejb-relation-name>Employee-User</ejb-relation-name>
<ejb-relationship-role>
<ejb-relationship-role-name>Employee-May-Have-User</ejb-relationship-role-name>
One
<relationship-role-source>
<ejb-name>EmployeeBean</ejb-name>
</relationship-role-source>
<cmr-field>
<cmr-field-name>user</cmr-field-name>
</cmr-field>
</ejb-relationship-role>
<ejb-relationship-role>
<ejb-relationship-role-name>User-Belongs-To-Employee</ejb-relationship-role-name>
One
<relationship-role-source>
<ejb-name>UserBean</ejb-name>
</relationship-role-source>
</ejb-relationship-role>
</ejb-relation>

Then, jbosscmp-jdbc.xml looks like:

<ejb-relation>
<ejb-relation-name>Employee-User</ejb-relation-name>
<foreign-key-mapping/>
<ejb-relationship-role>
<ejb-relationship-role-name>Employee-May-Have-User</ejb-relationship-role-name>
</ejb-relationship-role>
<ejb-relationship-role>
<ejb-relationship-role-name>User-Belongs-To-Employee</ejb-relationship-role-name>
<key-fields>
<key-field>
<field-name>id</field-name>
<column-name>A14_id</column-name>
</key-field>
</key-fields>
</ejb-relationship-role>
</ejb-relation>

And SQL for Postgresql is:

create table A00_Employees (
A00_id SERIAL not null,
A01_id INT4 not null,
A07_id INT4 not null,
A14_id INT4 null,A15_id INT4 not null,
A00_forename VARCHAR(80) null,
A00_surname VARCHAR(80) null,
A00_patronymicName VARCHAR(80) null,
A00_birthDate DATE null,
A00_isDefault BOOLEAN not null,
constraint PK_A00_EMPLOYEES primary key (A00_id),
constraint FK_R00_EMPLOYER foreign key (A01_id)
references A01_Companies (A01_id),
constraint FK_R01_ADDRESS_BOOK_ENTRY foreign key (A07_id)
references A07_AddressBookEntries (A07_id),
constraint FK_R02_USER foreign key (A14_id)
references A14_Users (A14_id),
constraint FK_R03_EMPLOYEE_POSITION foreign key (A15_id)
references A15_EmployeePositions (A15_id)
);

create table A14_Users (
A14_id SERIAL not null,
A14_username VARCHAR(25) not null,
A14_password VARCHAR(25) not null,
constraint PK_A14_USERS primary key (A14_id),
constraint AK_USERNAME_A14_USER unique (A14_username)
);

So, there is no FK in A14_Users on the table A00_Employees. And If I used BMP instead of CMP, I could easily locate EmployeeBean by user id and UserBean by employee id.
But JBoss throws SQL exception on attempt to load instance of UserBean:

ERROR: Attribute "employeebean_user" not found.

So, seems like JBoss can not handle such a kind of CMR, when there is only one FK in 2 tables that are used by 2 CMR beans.

THank you for your help!