DataSocket Error when Used with Multi-thread

When I used DS_SetDataValue() function in the thread A that started instantly after openEX() function to connect with the DataSocket Server, the Server could receive the data and the DS_SetDataValue() function of client ran correctly. But when I ran DS_SetDataValue() function in the thread A that started long afer the connection with DataSocker Server (that is to say I ran a data acquiring callback function between the connection and writing operation to the DataSocket Server, and the thread A was started at the end of data acquiring callback function), there always was a error "NON-FATAL RUN-TIME ERROR:   "cam.c", line 1087, col 13, thread id 0x000008BC, function id 1:   Function DS_SetDataValue: (return value == -2147024809 [0x80070057]). 参数不正确。" 

Any ideas why this happens?

Thanks!