Well, this is not a problem but the way Session Beans work. Each method call from client is an individual call and the session bean considers them to be 2 different clients, for simplicity.
When the first method id called, a session bean object is pulled from the pool, services the request and is then sent back to pool, you can think of it on similar lines to being GC. When you call the SB next time, any SB object can be called from the pool and this will have everything given to it fresh, including your hashtable.
If, you need to populate data into a hastable in one call and use it another then you can cache the hastable on the client side and not on the bean side. There are several ways to achieve the same including using the Server's cache, if it provides one or simply creating a hastable in your client code and then passing it to second method.
Hope this clears things and is useful to you.