Updating passwords via this API is disabled for security reasons. Use the resetPassword API instead

Question

Some of my users (actually only 2 of them) are getting an error which I described at subject when they want to login into stackmob. Why do we get this error?

public void createUser(final User stackmobUser) {
    stackmobUser.save(new StackMobCallback() {
        @Override
        public void success(String arg0) {
            login(stackmobUser);
        }

        @Override
        public void failure(StackMobException arg0) {
            Toast.makeText(getApplicationContext(), "user has not been created because of: " + arg0.getMessage(), Toast.LENGTH_LONG).show();
        }
    });
}

here is the exception they gave:

com.stackmob.sdk.exception.StackMobHTTPResponseException: call failed with HTTP response code 400, headers Date=Mon, 11 Mar 2013 15:27:51 GMT, Content-Type=application/vnd.stackmob+json; version=0, Connection=close, Content-Length=122, body {"error":"Updating passwords via this API is disabled for security reasons. Use the resetPassword API instead."}