Hi Chris photosw,
Sorry for the inconvenience.
As you said that uncheck of Graphic processor fixed that for you.
It seems to be an issue with Graphic card driver.
Either the driver is corrupt or not compatible with the Lightroom version or the Operating System.
I recommend you to check for updates of the graphic card driver.
Though MAC provides the graphic card update automatically but I believe this update is not working for your Lightroom.
Many thanks for your reply, Much Appreciated... I am trying to check on that now, Looking like a trip to an Apple shop!!!
Thanks for the reply.
Surely if needed visit that.
But I believe if you will google about the updates you will be able to find that.
Best way is check the graphic card manufacturer website for any update.