In the last couple of weeks something started happening in TWO PCs around here - both say "Windows Media Center cannot play this DVD" when I try to play a disc from a network storage.

These have been working for years and I'm pretty sure I even played a couple of them in the last few weeks.

Now, if I open the folder with VLC then all works fine. 

It could be some Windows Update causing trouble, but I don't remember seeing anything Media Center related in the last few months. All drivers are updated.

Any ideas? Preference is not to install third party codecs because a) never needed them before and b) don't want to mess up with Freeview|HD decoding.