opencv :: Multiple unwanted window with Garbage name

i am using opencv to capture video from webcam and display it in namedWindow.

cv::Mat rawImage;
cv::VideoCapture captureDevice;
captureDevice.open(0);
cv::namedWindow("webcam", 1);
bool running = true;
while(running)
{
    captureDevice >> rawImage;
    if(!rawImage.data)
    {
        continue;
    }
    cv::imshow("webcam", rawImage);
    char ch = cv::waitKey(33);
    if(ch == 'e')
    running = false;
}

initially code runs fine but after random (5 sec approx) period older named window freezes and new window with some garbage name pops up and start showing webcam images. this continues to happen and i am getting multiple unwanted named window. What is the reason for popping up for those unwanted windows?