Seam 3 TransactionInterceptor found No transaction in jboss 7 (web profile)

[yangju.richard.yang.pearson.com]

My code works fine in jboss 6 (deployed as ear). Recently we migrated our code to jboss 7 and deployed it as war. Now we got the following errors:
java.lang.UnsupportedOperationException: no transaction
     at org.jboss.seam.transaction.NoTransaction.begin(NoTransaction.java:47) [seam-persistence-impl-3.0.0.Final.jar:]
     at org.jboss.seam.transaction.DefaultSeamTransaction.begin(DefaultSeamTransaction.java:102) [seam-persistence-impl-3.0.0.Final.jar:]
     at org.jboss.seam.transaction.Work.workInTransaction(Work.java:51) [seam-persistence-impl-3.0.0.Final.jar:]
     at org.jboss.seam.transaction.TransactionInterceptor.aroundInvoke(TransactionInterceptor.java:188) [seam-persistence-impl-3.0.0.Final.jar:]

The code is something like this:
@TransactionAttribute
@ApplicationScoped
public class MyServiceImpl implements Serializable, MyService{
   
    @Inject
    @MyEM
    private EntityManager em;