Yes I do realise now that it's not a common issue, and that had it have been there would have been some responses. But of course I didn't know that when I posted! The trouble is, of course, that if it's not commonly experienced then finding a solution is likely to prove difficult. My follow up post is more for information really, to those 130 or so viewers.
The "other issues" I mentioned have also been referred to Phase One, and as both responses suggested uninstalling v7.1.4 and replacing it with v7.1.3 I was persuaded to undertake the exercise. And yes, I have tried disabling hardware acceleration, but that didn't make any difference either I'm afraid. They didn't suggest, and I haven't undertaken, updating the graphics drivers. I'll look into that, thanks.