Please see issue 117333 for additional info. I already fixed this for DD2beansDataObject in websvc/jaxrpcsupport, so if 
there are no other xml based data objects in the websvc modules you can just close this issue - at least I couldn't 
find any other ones under nb_all/websvc.

As for how to fix, you can use XmlFileEncodingQueryImplementation from xml/core. Basically you just need to add an 
instance of XmlFileEncodingQueryImplementation to the cookie set of a data object:

getCookieSet().assign(FileEncodingQueryImplementation.class, XmlFileEncodingQueryImpl.singleton());

and override the DataObject#getLookup() method:

    public Lookup getLookup() {
        return getCookieSet().getLookup();
    }