No values have been written. Details: could not insert: [USERROLEDT2804] (APNX-1-4208-004)

Interface Definition: Expression evaluation error: An error occurred while executing a smart service: An error occurred while trying to write to the data store [KONE_User_Development_Database]. No values have been written. Details: could not insert: [USERROLEDT2804] (APNX-1-4208-004)

I make a interface for new user to register, but once new user finish his information fill in and hit submit, the first time is good, all data inserted to back end without problem. However,if he click twice in submit button, always jump out report error as above.