Thanks Eric.
I have identified the cause of the problem and identified the solution.
It is one of those dumb things that crop up from time to time when you are working away, and is due to a setting within another application.
The problem and solution have has nothing to do with the editor. Although I will explain what happened below so that other editor users can avoid experiencing the problem.
I store a local up-to-date version of each page's code on my PC in a plain notepad file for security purposes and in case I stuff up the code within the editor and cannot for some reason recover it.
When previously recovering pages from these local back up files, I must have had Word Wrap turned off in Notepad. I must however at some time turned Word Wrap on. Then when I copied code from the backup notepad document and pasted that code into the editor HTML view, the code carried within it the hidden line wrap code which then became visible when the code was pasted into the editor.
Because some of the link url's within that code were long and so broke to a second line when Word Wrap was turned on in Notepad, the code snippet %0D%0A%0D%0A (which is the ASCII code for a line wrap), displayed within the URL, causing images to not display and causing hypertext links to become broken.
The simple solution, is to always ensure that Word Wrap is turned off in Notepad if you are copying code from that application and pasting it into the editor's HTML view.
Thanks
David