Hi all,
i have searched in whole internet to find a solution to my problem but nothing...
I have a servlet in Tomcat v6.0.32 that needs to invoke a remote EJB on Glassfiah v3.1. I have followed this official tutorial: EJB FAQ — Java.net
But I receive the following error:
Java Code: 
javax.naming.NoInitialContextException: Cannot instantiate class: com.sun.enterprise.naming.SerialInitContextFactory [Root exception is java.lang.ClassNotFoundException: com.sun.enterprise.naming.SerialInitContextFactory]
	at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:657)
	at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288)
	at javax.naming.InitialContext.init(InitialContext.java:223)
	at javax.naming.InitialContext.<init>(InitialContext.java:197)
	at mwt.j2ee.gescuola.client.TestServlet.process(TestServlet.java:47)
	at mwt.j2ee.gescuola.client.TestServlet.doGet(TestServlet.java:22)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:851)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:278)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:300)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassNotFoundException: com.sun.enterprise.naming.SerialInitContextFactory
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:247)
	at com.sun.naming.internal.VersionHelper12.loadClass(VersionHelper12.java:46)
	at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:654)
	... 23 more
I have included correctly the gf-client.jar needed library in my Eclipse project. If I try to create an object of class SerialInitContextFactory assigning it to a variable I receive the same error.
I have created a client for this EJB as a normal java client application (not running in Tomcat) and it works correctly.

Someone can help me?

Thanks!