unhandled memory exception problem

edit

i have made some corrections to your code and tested.

EDIT 1 : you can see the changes that i have made here

EDIT 2: you can see the changes that i have made here

final code is here

INITIAL ANSWER

you did not post all your code. i think it is modified from this code

i did a small correction on your code as below, please try it. if the problem persist please post all your code.

int main()

{

         CascadeClassifier faceCascade;
         CascadeClassifier eyeCascade1;
         CascadeClassifier eyeCascade2;

Rect faceRect;
VideoCapture videoCapture ("nn.mp4");



cout << "Face Detection ." << endl;
cout << "Realtime face detection using LBP " << endl;
cout << "Compiled with OpenCV version " << CV_VERSION << endl << endl;

// Load the face and 1 or 2 eye detection XML classifiers.
initDetectors(faceCascade,eyeCascade2);

Mat thresh, gray;
while (1)
{
     Mat frame;
     videoCapture>> frame;
     detectLargestObject(frame, faceCascade, faceRect);
     if (faceRect.width > 0)
     {      // modification is begin here 

     Mat faceImg = frame(faceRect);

     rectangle(frame, faceRect, CV_RGB(255, 0, 0), 2, CV_AA);

     Mat gray;
     if (faceImg.channels() == 3) {
         cvtColor(faceImg, gray, CV_BGR2GRAY);
     }
     else if (faceImg.channels() == 4) {
         cvtColor(faceImg, gray, CV_BGRA2GRAY);
     }
     else {
         // Access the input image directly, since it is already grayscale.
         gray = faceImg;
     }

     Point leftEye, rightEye;
     Rect searchedLeftEye, searchedRightEye;

     detectBothEyes(gray, eyeCascade1, eyeCascade2, leftEye, rightEye, & searchedLeftEye, & searchedRightEye);

     rectangle(faceImg, searchedLeftEye,Scalar(0, 255, 0), 2, 8, 0);
     rectangle(faceImg, searchedRightEye, Scalar(0, 255, 0), 2, 8, 0);

       searchedRightEye.y += searchedRightEye.height / 3;

       searchedRightEye.height -= searchedRightEye.height / 3;

      Mat eye_region=faceImg(searchedRightEye);

     cvtColor(eye_region, gray, CV_BGR2GRAY);

     threshold(gray, thresh, 60, 255, THRESH_BINARY);


     imshow("eye_  video", thresh);
     }  // modification end

     imshow("video", frame);
     // Press 'c' to escape
     if (waitKey(30) == 'c') break;
}

return 0;
}