Unable to sign in on itunes and go to the itunes store on my pc

For the last one week whenever I fill in my apple ID and password to sign in the itunes store on my windows pc a dialog box with the message "We could not complete your itunes request. Your network connection timed out" is displayed." which is followed by another message "We could not complete your itunes store request. An unknown error occured(-50)." My laptop is connected to the internet and all network related tasks occur smoothly. So why does it display such an error?