Video player problems with 8.1

Is anyone else getting problems with video playback?

I can't seem to play .mp4 files in either the Metro Video app or in Windows Media Player. Tried installing a codec pack and that just let me play the video without audio in Media Player Classic.

I checked that there were no driver updates for my graphics card, but Intel says it's up to date. I had no problems in the 8.1 preview.

I'm using a Lenovo Yoga 13.