Exception in Sender mail module

Hello

We have developed a mail module but we´re facing some problems. The module only process the first mail message. After the second "run", it throws the exception:

exception caught during processing mail message[1]; com.sap.aii.af.mp.processor.ModuleProcessorException: Error during processing local bean: localejbs/MyModule caused by: com.sap.engine.services.ejb.exceptions.BaseEJBException: Exception in method process.

The module starts working again only by restarting java stack on scmicm. Even if I stop and start the Communication Channel on Rwb, it doesnt work.

Any ideas?

Thanks!