Too many Metro Apps

Has anyone noticed what happens when you have more Metro Apps open than can fit in the task list down the left side? With me the screen flashes and the list is cleared and you end up on the start menu. The apps remain open in task manager though but you have to press the tiles to switch to them. That needs some work.

That happened to me today for the first time, probably because it was the first time I had quite a few apps open. I'm getting in the habit of closing down the ones I dont think I'll use again in the immediate future.
Its probably some memory thing and hopefully will be fixed.

I did some further checking. I have two VMs with Win 8 CP. It always does it in the VirtualBox VM but not in the VMPlayer one so it is not straightforward.