This is hard to describe, so I'll post a screen shot.

Once it happens it is difficult to make  the Start8 screen go way. It just pops up after clicking the start button and then doesn't go away. You can click again ont he start button, open other apps, hit the windows key, alt tab, it remains. Then for reasons I haven't been able to figure out yet, it will go back to normal.

Once I made it behave by typing in the name of an app I wanted to run. As soon as I started typing the misbehaving start windows went back to normal.

I am running VMware in Unity mode often. I haven't pinned down if that is related. (Unity options appear above the Start button location)

https://www.evernote.com/shard/s258/sh/55d491e4-994d-4cba-9992-cb4fe556902b/0b9e3a323a7138a0950c6e7acc7ca37a