java.lang.NullPointerException
    at flex.messaging.io.SerializationContext.getSerializationContext(SerializationContext.java:227)
    at ru.Utils.getSerializationContext(Utils.java:16)

public class SerializationContext {
  // ...

  private static ThreadLocal<SerializationContext> contexts = new ThreadLocal(); // line 207

  // ...

  public static SerializationContext getSerializationContext() {
    SerializationContext sc = (SerializationContext)contexts.get(); // line 227
  }
}

public class Utils {
  public static SerializationContext getSerializationContext() {
    SerializationContext context = SerializationContext.getSerializationContext(); // line 16

    // ...
  }
}

public static void releaseThreadLocalObjects()
{
       contexts = null;
}