This screen you are describing indicates that there is a program running that is telling Windows that it could not shut down cleanly. For example, if you have Microsoft Word open, it will pop up
with a dialogue box asking you to save your document. If you do not answer this box and the computer attempts to shut down, you will get the screen you are describing and it will show you that Microsoft Word is preventing the computer from shutting down.
In your scenario, taskhost.exe is the reported application holding up shutdown. There was a
known issue with Windows 7 with the issue you are describing. In Windows 8.1, you may merely be encountering a situation where your computers performance is slower than expected. You can stop background
applications from running, defragment your hard drive, and take other performance enhancing steps to help resolve the issue.
Brandon
Windows Outreach Team- IT Pro
Windows for IT Pros on TechNet