okay can you send complete error line? I suspect it says something like
The specified HTTP method is not allowed for the requested resource for content type application/xml, application/bla bla bla
also try to invoke the rest call with setting header value of
Content-Type to application/json or application/xml
I think your configuration is correct since you are not getting 404 which mean url is mapped to service but its just problem with mapping correct method.
how are you invoking the serivce? just pasting url in browser? to add headers I would suggest use RestClient a add-on for firefox.
let me know how it goes.
-P