two beans within single transaction problem

[beep_beep]

Hi!
I have very strange exception. I'm quite new in ejbs, so , please, be patient.
My bean (SfSB) called by servlet and invoked method on bean has attribute
TransactionAttributeType.REQUIRED.
Then my bean calls other SfSB bean(injected) and called method is also has
TransactionAttributeType.REQUIRED
On second call I have this annoying exception:

What is wrong here? I have no clue.
Please, help!!

javax.ejb.EJBException: java.lang.RuntimeException: cannot import a transaction
context when a transaction is already associated with the thread
at org.jboss.ejb3.tx.Ejb3TxPolicy.handleExceptionInOurTx(Ejb3TxPolicy.ja
va:69)
at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:83)
at org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java
:192)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInt
erceptor.java:76)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulIn
stanceInterceptor.java:81)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.aspects.security.AuthenticationInterceptor.invoke(Authentic
ationInterceptor.java:78)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterce
ptor.java:47)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(Asynchrono
usInterceptor.java:106)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.stateful.StatefulContainer.dynamicInvoke(StatefulConta
iner.java:308)
at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:104)
at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRem
otingInvocationHandler.java:82)
at org.jboss.remoting.ServerInvoker.invoke(ServerInvoker.java:828)
at org.jboss.remoting.transport.local.LocalClientInvoker.invoke(LocalCli
entInvoker.java:72)
at org.jboss.remoting.Client.invoke(Client.java:525)
at org.jboss.remoting.Client.invoke(Client.java:488)
at org.jboss.aspects.remoting.InvokeRemoteInterceptor.invoke(InvokeRemot
eInterceptor.java:55)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.aspects.tx.ClientTxPropagationInterceptor.invoke(ClientTxPr
opagationInterceptor.java:61)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.aspects.security.SecurityClientInterceptor.invoke(SecurityC
lientInterceptor.java:55)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.
java:65)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.stateful.StatefulRemoteProxy.invoke(StatefulRemoteProx
y.java:133)
at $Proxy87.create(Unknown Source)
at com.sap.xtp.client.simple.ClientServlet.doPost(ClientServlet.java:74)

at com.sap.xtp.client.simple.ClientServlet.doGet(ClientServlet.java:40)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:173)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFi
lter.java:81)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:178)
at org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrinc
ipalValve.java:39)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(Securit
yAssociationValve.java:159)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValv
e.java:59)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:856)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ssConnection(Http11Protocol.java:744)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpo
int.java:527)
at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWor
kerThread.java:112)
at java.lang.Thread.run(Thread.java:595)
Caused by: java.lang.RuntimeException: cannot import a transaction context when
a transaction is already associated with the thread
at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInt
erceptor.java:62)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulIn
stanceInterceptor.java:81)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.aspects.security.AuthenticationInterceptor.invoke(Authentic
ationInterceptor.java:78)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterce
ptor.java:47)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(Asynchrono
usInterceptor.java:106)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:98)
at org.jboss.ejb3.stateful.StatefulContainer.dynamicInvoke(StatefulConta
iner.java:308)
at org.jboss.aop.Dispatcher.invoke(Dispatcher.java:104)
at org.jboss.aspects.remoting.AOPRemotingInvocationHandler.invoke(AOPRem
otingInvocationHandler.java:82)

[beep_beep]

To clarify: I have CMT, and all other defaults. And I want one bean will be able to call another. And transaction should start in first bean and end in second.

[beep_beep]

Hmm...
I have changed second bean's interface to Local and this solved the problem.

But is it impossible to call Remote? Why does it happen?
Local beans can be in scope of single transaction and remote can't?

Why?

Pleeeeease, answer!