I don't think the monitor or computer is the problem. It's the same one I've had for a long time, and seems to work fine. (We're talking a period of about 3 or 4 years here.) And it's not all of the images, just some. I'm not sure at this point if there's a common denominator here.
Could it be something to do with bad sectors, or the result of defragging, or ??
Thanks for reminding me about the loss during saving, I had forgotten about that. (I think most of my editors are set to 95%). None of my editors ask me if I want to save them, unless I do some editing, which I haven't done to any of these for a long time.
It's not a big issue, just odd.