Also there is slight lag when clicking a window in the fullscreen preview. If I press win+z to open preview, then win+z again to close it there is no lag in the zoom animation.
It was a problem with D3DOverrider. Not sure why, but D3DOverrider dings when a 3D application goes fullscreen. Didn't make the connection until I launched a game and heard the ding. So closing D3DOverrider fixed the problem. Also fixed the lag issue.