On or about 12/9/2014, Microsoft released a Windows Update for all machines greater and equal to Windows 7, KB3004394.

If you have installed this update, I strongly recommend you remove it as soon as possible.

Through my own testing (and confirmation from various sites whose links I will post below) I can confirm two things:

1) Installing KB3004394 on a machine that has Media Center Extenders attached to it will break the extender functionality.
2) Installing KB3004394 on a Windows 7 machine -can- result in being unable to do any more Windows Updates.

Intrigued? Read on.

I installed KB3004394 on 12/9/2014, as part of my usual bi-weekly update schedule (and also because I was re-imaging my desktop).

I installed it on all my computers (1 Desktop, 2 Laptops, 1 Tablet, 1 HTPC) and on all of them running Windows 7 I started encountering major problems.

I installed it on my HTPC which has a Ceton Echo and an Xbox 360 as a Media Center Extender attached to it for the purposes of watching TV. After the update was installed, I found that upon starting the Extender, I would get the “Windows Media Center” screen and then nothing but a black display. I could still move about the menus (as indicated by the audio playing and what not) but you could not see anything. Uninstalling KB3004394 per these threads (One, Two) and all of a sudden my Extenders were working again.

I installed it on my Desktop which was just freshly rebuilt (I got in on a 480 GB SSD on Amazon!) and all of a sudden I could not install ANY other Windows updates because of error 800706F7.  Looking into the error code in Event Viewer and I saw that it was not able to communicate or properly secure the download of the new updates.  Thanks to my roommate Nick he found that a bunch of other people were having problems with KB3004394 preventing updates (One, Two, Three).  I uninstalled KB3004394 immediately and now my desktop updates properly.

It is very telling that Microsoft has already pulled KB3004394 from Windows Update — you cannot get it from there anymore.

That being said, they can’t fix it with Windows Update because you won’t be able to download any new updates.  You HAVE to manually uninstall KB3004394 to get it back.

Good grief.  Poor quality control and assurance at its finest.