After all available updates, whenever I click the new Deepin 15 button on the dock, which allows you to graphically switch between desktops, Deepin 15.1 immediately freezes, the only 'life' remaining being the mouse-pointer which you can move about, but clicking on anything has no effect.

This is where I and Deepin 15 part company, at least till this setup becomes usable.  Since the only way to exit from the above situation was to forcibly switch off the computer (which I did several times), I now have the additional major problem where Deepin willl (yet again!) not even boot normally - booting in recovery-mode, I am informed that after it tries to file-check the system (fsck), it encounters 'error 4' and cannot continue.  Second time the same thing has happened with Deepin 15, whereas there are no such boot-up problems from either WinXP or Win7, which also reside on the same SSD - so definitely a Deepin problem.