Security Prompt when trying to call a webhttpbinding service method.

i was working with a webhttpbinding service which was being called from Javascript and which inturn calls a wshttpbinding service, and all of a sudden i was getting a login prompt when i was trying to invoke this new method that i created, after a while i found out that the problem, my datacontracts were not updated, it was missing a new field that i added, once i added this new field, the login prompt went away....