I have had a spate of issues with Windows 10 computers recently, with symptoms such as not shutting down, not restarting, black screen on restarting, very, very slow running and a few others. The common thread in them all seems to be the download and install of the Windows 10 1511 upgrade, or the Windows 10 1511 updates which have been released recently. What seems to be happening in some cases is that the very large upgrade process (which can take several hours to download, prepare for and install) has been kicked off automatically, and possibly silently, so the users have no idea it is happening. I have fixed several computers by just powering down, rebooting and baby sitting the update process. In one case, the Windows Update Server appeared to be very confused, and had been in a fail/retry loop for several months! Stopping the wuauserv and bits services and clearing the update data bases helped in this case.
Annoyingly, it has also affected one of my machines! Well sort of. This morning my MYOB server machine stopped any access to the MYOB files. Some research revealed this was down to an issue with windows updates and MYOB. The proposed workaround was to remove a recent update to the Windows 10 system, in my particaular case one relevant to the 1511 update. However, when I did this, I rebooted to a black screen, the only way out of which was to do a system restore. I found if I went back beyond the last two sets of updates( both 8th March 2016) everything works fine again. Unfortunately, it is not possible to block specific updates or to stop updates in Windows 10, so it will all stop working again soon.
A black mark to Microsoft, this round of updates is definitely causing problems in some cases, which is a shame, because Windows 10 was doing so well.