Playback sounds normal, but the timeline seems to intermittently jump or stall when in playback. Latency set at 512.

That's could be you graphic card. 
Sometimes when I've had video glitches it was because I forgot to disconnect the internet and Windows was doing stuff behind my back. 

Agree with the points about the graphics card and video. I had a spate of this when I replaced my second monitor and adjusted resolutions. Other things to consider, even when you're not connected to the internet, are whether your antivirus s/w is still active or something like a dropbox is still active in the background.

Pause key toggles CPU Conservation Mode that restricts GUI updates to once per second.

Turned off my anti virus and that did the trick. Thanks

brundlefly
Pause key toggles CPU Conservation Mode that restricts GUI updates to once per second.

Omg thank you.