Why is my Start Menu and Cortana not opening on Build 10074 after working once or twice per reboot?

[apoc527]

Basically, for no apparent reason, my Surface Pro 2 running the 10074 Insider Preview will lose the ability to open the Start Menu or Cortana. Super annoying.

 

[Funky Cricket]

I was having the same issue before the most recent updates to 10074. I haven't had it since, but I haven't spend much time on my test box as I've been traveling for work.