iCloud and Windows 10 compatibility issue
I just spent a few hours troubleshooting a 48 hour old install of Windows 10 onto an HP Probook 6470b. Long story short, even though everything had been fine, today upon boot I noticed iCloud Photos reported a pop-up stating it did not have permissions to access. After that, the Windows desktop and system tray kept refreshing every 2-3 seconds, and I had no control over the Start Menu button on Windows (nothing would happen even if the flashing stopped); and once the flashing did stop (though no idea why it stopped) I also could not launch the IE replacement "Edge," as it errored with an inability to register.
Running Windows sfc did not help.
From Task Manager, turning off iCloud caused the flashing to cease.
I also found if I turned off Wi-Fi and rebooted, the system would boot without the desktop refreshing, but as soon as I enabled Wi-Fi it began to flash again.
A repair of iCloud was of no use.
REMOVAL of iCloud cleared the issue; I am on the laptop now, with no noticeable problems.
iCloud was version 4.1.1.53. I cannot determine what the current version is, so I am not going to bother with it, but it appears, at least in my case, that iCloud's version is not compatible with Windows 10.
iPhone 6, Other OS, Verizon iPhone 6