Try to trigger a restart by pressing the power button once. If it won't work after several attempts, rightclick on the Task Bar to select Task Manager and under Applications first tab highlight Windows Updates service to End Task.
If all else fails, hold the Power button down to hard shutdown. Then reboot to try Updates again, using smaller groups so that you can isolate the update responsible if the problem recurs. Open a WUD support case on the WUD website which is by email and reliable though not that fast.