Anybody saw this exception :

javax.transaction.TransactionRolledbackException: Unable to deregister with TransactionManager: java.lang.IllegalArgumentException: null xaRes; nested exception is:
java.rmi.RemoteException: Unable to deregister with TransactionManager: java.lang.IllegalArgumentException: null xaRes
java.rmi.RemoteException: Unable to deregister with TransactionManager: java.lang.IllegalArgumentException: null xaRes
at br.com.hpg.sfragata.sql.bean.SQLBean.executeQuery(SQLBean.java:36)
at java.lang.reflect.Method.invoke(Native Method)
at org.jboss.ejb.StatefulSessionContainer$ContainerInterceptor.invoke(StatefulSessionContainer.java:570)
at org.jboss.ejb.plugins.SecurityInterceptor.invoke(SecurityInterceptor.java:190)
at org.jboss.ejb.plugins.StatefulSessionInstanceInterceptor.invoke(StatefulSessionInstanceInterceptor.java:209)
at org.jboss.ejb.plugins.TxInterceptorCMT.invokeNext(TxInterceptorCMT.java:133)
at org.jboss.ejb.plugins.TxInterceptorCMT.runWithTransactions(TxInterceptorCMT.java:263)
at org.jboss.ejb.plugins.TxInterceptorCMT.invoke(TxInterceptorCMT.java:99)
at org.jboss.ejb.plugins.LogInterceptor.invoke(LogInterceptor.java:195)
at org.jboss.ejb.StatefulSessionContainer.invoke(StatefulSessionContainer.java:326)
at org.jboss.ejb.plugins.jrmp.server.JRMPContainerInvoker.invoke(JRMPContainerInvoker.java:482)
at org.jboss.ejb.plugins.jrmp.interfaces.StatefulSessionProxy.invoke(StatefulSessionProxy.java:150)
at $Proxy6.executeQuery(Unknown Source)
at jsp._0002fjsp_0002findex_0002ejspindex_jsp_3._jspService(_0002fjsp_0002findex_0002ejspindex_jsp_3.java:84)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspCountedServlet.service(JspServlet.java:130)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:282)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:429)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:500)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:405)
at org.apache.tomcat.core.Handler.service(Handler.java:287)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:213)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:501)
at java.lang.Thread.run(Thread.java:484)


what is "null xaRes"