Looks like I'm talking to my self!
Well, the problem does not appear to be theme related. I have just replaced my tweaked theme (tweaked for font type, wrapper width, image size) with a new virgin TwentyTen by doing it via Dreamweaver FTP thus:
Local: renamed TwentyTen(local) with no Dreamweaver link update...
switched to remote view (server)
Remote: downloaded TwentyTen and renames to TwentyTen(server)
That gives me safe copies....
Then copied a virgin TwentyTen theme from the WordPress download and pasted it in my Dreamweaver sites directory alongside the two renamed safe copies. and uploaded to the server.
On viewing my WordPress site, it had changed back to the specs of the untweaked version (Sans-serif, narrower wrapper, narrower images) exactly as expected...
Then I went into my WP Admin and still have the original problem: No text entry box on PAGE mode (Edit Page Or New Page)
It seems to have stopped at exactly 100 pages - Is this a limit on quantity of pages? I don't think so because of the server error 500.
If there is anyone out there who can give me a clue as to what to do next I would dearly love to have some feedback.