Same problem here on Windows 10; just started happening yesterday and very annoying.
I can't click on anything in Windows from startup -can't left or right click the taskbar or start menu.
I can however rightclick on the desktop and leftclick in the menu it opens. I can also leftclick and drag to make a selection box. But left clicking on the desktop itself does nothing.
Also, if I open a window from the start menu with tab/directional keys and enter, then left click on the window it deselects the window as others have said.
It's as if there is a large invisible layer on top of all windows and left click selects it (deselecting everything else).
As others have said, opening and closing task manager fixes the problem.
As my mouse still works and left clicks are causing things to happen I can't blame my mouse hardware/software as my inputs are recognised. This seems to be a Windows problem. Would like someone from Microsoft to post here with a fix as this has been a problem
for almost a decade!
