My SP4 recently installed the latest big Windows update. Ever since then, I can't compose messages like this one on another message board I frequent. When I tap in the text input area to compose, the cursor does not appear. When I hover the Surface pen over the text input area, I get the spinning wheel. If I type, words appear, but the navigation is partially disabled, so I can't edit the text. For example, when I tap in the text area to move the cursor, nothing happens. What's going on?