Thanks for that link. I'll have a shot at the ESR version tomorrow because it's 0230 here now!
When I get the problems with Flash content it's for ten minutes or more at the start of a browsing session. When it happens the window for the clip flashes a very brief image of the start of the content and then goes black and stays that way for quite a few minutes but my Windows (yes, W7 Ultimate) remains perfectly responsive and behaves normally in every way provided I don't expect anything with Flash to show anything but a black image.
Once Flash starts to work after say ten minutes, it works perfectly and without delay for that original clip and for any others.
Grrr! Perhaps it's a sign that I should be reading a good book instead!