Here’s a quick tip: If you’re a Netflix subscriber and are having problems with the WatchNow feature, take a look at whether you have any caching proxy servers between the PC you’re using to watch a show and the Netflix servers (yes, that’s a long path and a very general statement, I know).
If, for example, you have a home network server with a caching proxy feature, try turning the proxy feature off. That helped me with MediaError(1400) problems, anyway.
If your ISP has a caching proxy, see if there’s a way around it, too. It may be a source of problems.