Transaction Required Exception in EJB Client

[kickmetoandy]

Hello,

i am getting a javax.transaction.TransactionRequiredException: Transaction Required when i try to access (finder method call)
my ejb cmp beans from a ejb client.

In my client i am using the UserTransction to handle transactions :

tx = (UserTransaction) jndiContext.lookup("UserTransaction");
 tx.begin();
 .....
 acces to my cmp bean
 ....
 tx.commit();

This works fine, when i access my cmp beans on a single jboss. however
if my cmp beans are deployed in a jboss cluster im a getting the Exception
above, accessing my cmp beans. The transaction type for my cmp beans
is "Mandatory", i am using jboss 3.2.7.
What can be the cause of my problem ? Is it possible that it has something
to do with distributed transactions ?

any ideas ?

thanks in advance,
Andreas