OpenCV video freezes

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I just installed opencv 3-dev. I then ran a simple code of a normal video capture which outputs the video taken from the webcam. But as soon as the program window opens the video freezes. It sometimes runs and sometimes hangs. I currently have found no solution. My code is as follows

import numpy as np
import cv2
cap = cv2.VideoCapture(0)
while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()
    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    # Display the resulting frame
    cv2.imshow('frame',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

This is the code! I hope you help me! Thanks in advance!! :)