The SFSB is passivated after the period specified in "Cache Idle Timeout" (or the corresponding definition in your sun-ejb-jar.xml). The passivated instance is removed from disk after the period specified in "Removal Timeout" (or the corresponding definition in your sun-ejb-jar.xml).
I suspect that the second time you tried to access the bean was after the removal timeout, so you'd want to consider making it bigger.
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