A Microsoft file hosting and synchronization service.
I have Malwarebytes installed too on both machines. I did cross my mind that antivirus or MWB might be doing something here - but having checked the logs of both, there is no visible record of either taking any action here.
It must be a possibility..... but it still needs fixing. I don't think I want to run without MWB installed...
I wonder if it's worth those of us on this thread stating what AV they have? I run Norton Internet Security and Malwarebytes on both machines - and Norton WiFi security on the laptop, but not on the desktop.
Quite frustrating.