Very many thanks Michael, your last suggestion proved to be the answer.
I checked 'Record/Playback in Settings and it was set on Auto.
When I altered it to SIMPLE, hey presto, it worked perfectly playing video as normal.
What I cannot understand is WHY have such a setting as Auto or Standard at all as they only play as stills.
Surely the point of a VIDEO editing programme is movement!
At the very least, surely it should flag up a warning when selected that it will only show stills?
However, I am delighted to get back to normality and I will be VERY careful what I select in future!
Once again Michael, many thanks.
Best wishes, George Duncan.