Thanks for your effort SndCastie - Interesting that your display is different from mine.
I looked again and have more information.
It must be some sort of automatic picture resizing issue.
After opening the window, firefox very briefly
displays a large box outline where the image is to go.
Then firefox reduces the box to just one or two pixels high,
so that the image just appears as a single thick line across the screen.
If I hover the mouse over the line/image so that the cursor changes shape to a hand
and then click, then the full image displays normally in a new window.
Also, clicking "zoom in", which is easier to do, does the same thing.