Arduino board+Labview, serial port communication problem

Hey guys, I met a problem in using VISA serial port communication module. I use arduino board to simply generate a number 350:

int value=350;

void setup(){

Serial.begin(9600);
}

void loop(){

Serial.println(value);
delay(250);

}

If you can watch the video, you can find that if I highlight execution and run the system, labview can receive data correctly. But if I don't highlight exection, labview goes wrong, sometimes it receives 350, sometimes it receives 50, sometimes it cannot receive anything.

And sometimes an overrun error occurred.

Could you please help me check where I made mistakes?:smileysad:

video