JAXB in java 1.6_03 vs java 1.6.0_13 and above

Question

I am trying to map a field of type List in a class, and I am using a XmlAdapter for this purpose eg

@XmlRootElement
public class A
{

@XmlJavaTypeAdapter(BListAdapter.class)
private List<B> bs;

}

this works fine in java 1.6.0_13 and above. In java 1.6.0_03 , I am getting a classCastException, B cannot be cast into a List.

I am not sure why this code does not work in the older version of JDK.