Attached is a simple EAR application with EJB, Web and application client module which invokes an EJB method.

Deploy it to the server. Then run the application client:
%JBOSS_HOME\bin\appclient.bat C:\Temp\Stateless.ear#StatelessClient.jar

On the client side, after the status output of the ejb call, I see this console output. It ends with a NullReferenceException.

21:33:39,065 INFO [org.jboss.ejb.client.remoting] (Remoting "endpoint" task-2)EJBCLIENT000016: Channel Channel ID d24023d4 (outbound) of Remoting connection 0c25db92 to localhost/127.0.0.1:4447 can no longer process messages
21:33:39,112 INFO [org.jboss.jaxr] (MSC service thread 1-3) JBAS014002: UnBinding JAXR ConnectionFactory: java:jboss/jaxr/ConnectionFactory
21:33:39,143 INFO [org.jboss.as.server.deployment] (MSC service thread 1-1) JBAS015877: Stopped deployment null (runtime-name: StatelessEJB.jar) in 41ms
21:33:39,143 INFO [org.jboss.as.server.deployment] (MSC service thread 1-1) JBAS015877: Stopped deployment null (runtime-name: StatelessClient.jar) in 53ms
21:33:39,143 INFO [org.jboss.as.server.deployment] (MSC service thread 1-1) JBAS015877: Stopped deployment null (runtime-name: StatelessWeb.war) in 56ms
21:33:39,159 INFO [org.jboss.as.server.deployment] (MSC service thread 1-3) JBAS015877: Stopped deployment Stateless.ear (runtime-name: Stateless.ear) in 59ms
21:33:39,159 INFO [org.jboss.as.controller] (MSC service thread 1-1) JBAS014774: Service status report
JBAS014776: Newly corrected services:
service jboss.remoting.endpoint.subsystem (no longer required)

21:33:39,159 INFO [org.jboss.as] (MSC service thread 1-2) JBAS015950: JBoss AS7.2.0.Alpha1-SNAPSHOT "Steropes" stopped in 35ms
21:33:39,159 ERROR [stderr] (Thread-38) Exception in thread "Thread-38" java.lang.NullPointerException
21:33:39,159 ERROR [stderr] (Thread-38) at org.jboss.as.appclient.service.ApplicationClientStartService$2.run(ApplicationClientStartService.java:156)
21:33:39,174 ERROR [stderr] (Thread-38) at java.lang.Thread.run(UnknownSource)