Help, rmi:multi thread client

I am developing a rmi program. Each client thread obtains the remoteObject by calling Naming.rebind().
My problem is when 20 client threads get the RemoteObject at the same time, i get the exception from naming.rebind()method.
Anyone can help me?
thanks

that is the exception i get
java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is:
     java.io.EOFException
     at
sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:203)
     at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:350)
     at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
     at java.rmi.Naming.lookup(Naming.java:84)
     at arch.lib.CommProxyImpl.setRemoteProxy(CommProxyImpl.java:52)
     at arch.ClientThread.<init>(ClientThread.java:45)
     at arch.ClientGenerator.main(ClientGenerator.java:27)
Caused by: java.io.EOFException
     at java.io.DataInputStream.readByte(DataInputStream.java:333)
     at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:189)
     ... 6 more

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