In fact you have been a great help by highlighting related issues and also pointing our areas for further research.
I'm just unsure if the problem is a one off, if something has become corrupt in the current Moodle code, if another install of the same environment on the same Windows platform would resolve the issue or if its just a bug with what is now an old version of Moodle that could be caused by a various reasons that will be resolved in the newer versions.
Admittedly I have only seen the error mesage in its initial form, I haven't turned debugging on or any other troubleshooting techniques and procedures to see if it could be quickly resolved by some means, I just thought I would post the message to see if it was already known.
As a bit of something extra I came across
https://moodle.org/mod/forum/discuss.php?d=200498 and https://moodle.org/mod/forum/discuss.php?d=200601.
This has a link to the the info you previously provided me with. They specific the problem being with grid format and refer to it as being a plugin. As far as I'm aware, no extra course plugins have been installed on my installation if this does turn out to be the issue. I didn't even know that extra course formats could be added on top of the standard install?
Thank you for your time and patience,