Relevance of these posts is that it all happened after "Never 10". May be no connection at all.
EDIT Mistake corrected above. It was Ccleaner and not FF that I suspected MS of sabotaging. In a way they did, because when Ccleaner finally working it took half an hour to clean 3.5 Gb of stuff - which I suppose is why the Run Cleaner button was greyed out for so long.
I have no idea what MS are playing at.