Model Driven Development under JBoss Transaction Service

Using JBoss 5.1, I am able to deploy the model and can see the getAll() results in the dataGrid, however when trying any CRUD operations, I get

org.hibernate.TransactionException : JDBC commit failed and

java.sql.SQLException: You can not commit during a managed transaction

what do I need to change in Jboss configuration so that the CRUD operations using model driven development work...