Yes, stock quotes are unavailable since yesterday with a "Referral Denied" error. This implies that NSE has made some changes over the weekend. However, if you browse NSE normally and look for quotes of a stock, they are available.
Using the referrer as a check is typically done by websites that do not want other sites to "steal" content or images. I have not yet determined how well the referrer check is done, but if done simply it is easy to spoof as it is a value sent by the user browser. You may recall that earlier, QT would parse the individual stock quote pages. Around Sep 22 last year, NSE changed the page behavior to use Ajax based data fetches. As a result, QT was updated to use the Ajax fetch -- this was very much cheaper on the NSE servers and bandwidth. Now, QT would either have to spoof the referrer (assuming it is done simply) or revert back to parsing the individual stock pages. My guess is that QT is unlikely to take the first approach.
There are other aspects that QT users should be aware of resulting from TD Ameritrade taking over QT, and the Medveds' contract being over and leaving Ameritrade. Earlier, QT was famed for its speed of support and updates. Now, users are complaining that support emails take a few days to be answered. As an example, I have sent a mail about NSE's problem to QT yesterday (I have a paid copy) without response so far. In contrast, QT support's response could be expected within an hour or two earlier, day or night. Secondly, other have mentioned that for Ameritrade, QT is low priority product with ThinkOrSwim having preference.
To cut things short, my view is that it is time to look for a QT replacement. Supporting NSE quotes is a feature that gives AmeriTrade little income, and perhaps some headache. The question is what is a potential QT replacement?
