
KG, & Dr. C
Here's what I'd do - download the MSE install from MS and put it somewhere safe. Isolate the PC from the network. e.g. disconnect the ethernet cable, disable the wireless connection. Uninstall MSE via the control panel. Turn off the firewall, see ==>>
Turn Windows Firewall on or off - Windows Help
Reboot - if the problem doesn't go away then at least you'll know what the cause isn't -- see 2 below
If it goes way, then re-enable the firewall and reboot, if the problem comes back it's a firewall issue. If not then reinstall MSE and reboot. If the problem comes back it's a problem with MSE, if not then maybe its fixed.
I saw something recently where a problem 'went away' after reinstalling the AV (can't recall which AV)
2 Problem exists after uninstall MSE and disable firewall
Re-enable the firewall, reinstall MSE, reconnect network.
Is calibre in your start up tasks, if it is then disable it from there. Then try starting calibre manually after a reboot once the other startup tasks are up and running.
The order in which tasks are executed at startup is a bit of 'catch as catch can' affair. Perhaps something has changed which has upset the apple cart - like the Windows 10 offer in the tray.
There are utilities that allow you to serialise and insert delays between starting tasks, I used one of them on Vista when two startup tasks were competing for the same resources - IIRC the problem went away when I moved to Win7.
Added : my experience is that 'disabling' MSE via its settings panel doesn't always survive a reboot. The only sure way I've found is to uninstall and reinstall it - sadly there's no export/import of settings - so screen shot your settings before you uninstall.
BR