(already solved by itself, as I was writing this post... ah, murphy...)
So I had an issue with the Grammer Help window, which wouldn't show.
Looks like an init issue, which may have been solved by trying one of the other windows (I'd say TERPs, since it's the only one I hadn't already tried before).
Now it works fine, even after restarting the program, so don't spend too much time on this, as this issue is unfortunately not reproductible on my end, sorry...
But maybe it can help new users, so I post anyway :)
--
My original message:
