For the past couple of days when I would shut down my windows 8.1 machine I would notice that the process would pause because "task host is busy stopping background processes". I'm would then have to kill it before it would go on to shut down .
Checking around the start up lists didn't bring anything and my av scanners had nothing to report. Searching was also not that helpful and now I couldn't even update the machine to the next version.
Having tried everything I figured why not turn off the last thing that was turned on which was sky drive sync and with that the problem went away . Turns out the sync was doing something even blocking the windows update manager .
Hopefully this helps others facing the same problem