Looks like the updates for today (10th Feb 2015) has an update that isn't installing correctly.
KB3001652 Update for Visual Studio 2010 Tools for Office Runtime.
On Windows 8.1 machines it seems to just hang.
However on a Windows 7 machine, I got a runtime installer appear, which required me to click through a few steps to install.
Therefore it looks like it is hanging because the setup installer is hidden in the background.
This was further confirmed by trying to reset the Windows Update system using my script from here: http://wuauclt.info/scripts.asp
In the command prompt window it said that a file couldn't be deleted because it was held open by another process.
Looking in Task Manager, I found a setup.exe process running. Killing that process immediately brought up the Reboot now windows in Windows Update. I ran the script again and it was successful. A reboot also passed without incident, taking just a couple of minutes which was normal for the VM I was using.
As the lab system I am testing against uses a WSUS, I declined the update. For home users, you should probably hide it. I expect it will get pulled by Microsoft very shortly.
So the complete method to deal with this stuck update.
1. In task manager, find the setup.exe that is running in the background which you cannot see and end the task.
2. Run the script from my web site above, to clean out Windows Update.
4. Re-run Windows Update. When you see the update listed, hide it.
Install all other updates as normal and reboot.