If you’re using Windows Media Center on Windows 7 with a CableCard tuner don’t install Windows Update KB3004394, the update is breaking playback of protected content(DRM). This doesn’t affect Windows 8 users and those using non-CableCard tuners. If you’ve already installed it or it’s automatically been installed, just go into your control panel and uninstall it. Anything recorded that fits under protected content won’t play on your computer with the KB3004394 update installed.
Big thanks for the notification via SiliconDust’s twitter.