Just for people's info.
I spent yesterday evening struggling with the non-working Start menu for build 1709 (as per above posts). When I came in tis morning, I started up and was immediately able to get the Start menu fully working. Yay. Wondered if there had been some invisible patch or something
However, to check, I did a restart and it was back to failing again.
What I finally realized was that I had started my machine and left it at the start screen while i made breakfast. I distinctly heard a notification come through (it turned out to be a new Java update), then when I logged in, I was able to get the Start menu perfectly. I tried a few restarts, not waiting, and the Start menu failed each time. So I tried to leave it...