Soap UI Error on Post Json

hi
I am using Rest service call on Soap UI , for Get I am getting Json out put but when I try to post I am getting an error "[CDATA[Internal Server Error: java.util.NoSuchElementException: None.get]]></data>" . I try to use the same post url on Rest client tools and it respond back json. but i don't know way I am getting an error on soap UI , any idea?

Thanks
~mathyas