KenK2
Your workaround does kill the "start button", but does not resolve the popping to gray screen in the last Mac spaces issue, which is the big Coherence problem. However it is noteworthy that when you prevent the start button (AKA ShellExperianceHost) from running, you can still right click on the start button location and get a context menu for essential tasks like shutdown/restart. The gray screen issue is the new Cortana search function which seems to have replace the historic search function. If someone knows how to disable Cortana in favor of the old search, the gray screen problem would probably not happen. Cortana must not conform to the historic Windows standards. I've also noticed that the gray screen will often show nonfunctional images of other Win apps I'm running, like Outlook, for example.