GARY30 HOORAY! i found the problem on my machines.
I use an InputManager called CosmoPod with Safari. I happened to install CosmoPod's verson 3.1 update over my previous version 3.0.1 and the problem went away! Just to be sure, I uninstalled CosmoPod entirely. No Porblems. Reinstalled the downrev version 3.0.1: Problems. And then reinstalled the CosmoPod update 3.1 and...NO Problems.
This is sweet, because I don't need to make a compromise. It would have taken weeks to figure this out, and Mike has been unable to replicate the problem on his equipment. So it's down to CosmoPod on my machine, and we need to keep a weather eye out for other InputManagers I suspect.
(Version 2.8.5)