WMPlayer 11 vid playback freezes, then speeds up

I've been having a bit of an issue running HD content.

Recently, I've been running many 1080p .mkv video files in Windows Media Player 11 with the help of the K-Lite codec pack. Last night though, one particular video was playing normally up until a certain point, when suddenly the video froze for a couple of seconds, followed by it speeding up to catch up with itself. All the while, the audio track continued as normal.

Any reason why this may have happened? It's been stumping me all night. Is there perhaps, another, more superior media player I should be using? (Media Player Classic and VLC both gave me inferior performance, by the way)

You should try another video player (I would suggest MPC-HC or VLC), but from what you've described I suspect that there was simply an error during the encoding process of the video or some other kind of a bug while the video stream was processed. I've rarely seen it happen with HD content, but it's not impossible.

Windows Media Player 12 comes with Windows 7. Did you purposely change to WMP11?