Sorry, I'm a newbie and won't be any help beyond that!
I get the 'editable' fields showing, but I can not click them or activate them and yes, EDIT bar is no longer showing in any browser?
If you check in your theme folder you will find a folder named elements, in there is your footer.php file. Open it and make sure its there, if not add it, and you should be right as rain,
And if I want to add that line, how do I do so?
Your page has several html snippets that call content from other sites, and scripts so these scripts can conflict with C5. When adding these snippets you can usually tell right away that there is a conflict, but every once in awhile the site or widget that your using updates its scipts, just like c5 updates, and if there are script conflicts with the widget updates, than it will automagically mess with your site.
There are several ways of going about switching versions, and its up to you which works for you. If it were me I would copy the text content from page, and begin removing versions one by one, or I would just go back to page 1 depending on how easy it is to rebuild.
Its not pleasant, but this is one of the many potential hazards with html snippets.