When unmarshalling incorrect (e.g. letter characters when float is expected)
data , JAXB tries to consult com.sun.xml.bind.v2.runtime.reflect.opt.Const for
acceptable default values to set, which results in IllegalAccessError because
the access is done from what appears to byte-enhanced code in the customer's
class/package, and Const is package protected.
Was able to solve the problem by making Const and its properties public.
See http://forums.java.net/jive/thread.jspa?messageID=260342 for some additional
details, including the stack trace.