These are the 3 WSHost.exe files I have on my Windows 8.1 64-bit machine. The one in C:\Windows\WinStore is the most important. Do you have a copy of that one in that location?
WSHost.exe C:\Windows\WinStore 25,304 28/11/2013 2:36:30 AM 15/01/2014 7:22:33 AM 26/01/2014 3:32:16 PM A exe
WSHost.exe C:\Windows\WinSxS\amd64_microsoft-windows-store-client-ui-wshost_31bf3856ad364e35_6.3.9600.16384_none_04418e7c83ec6c33 7,192 15/01/2014 4:14:38 PM 22/08/2013 8:53:06 PM 26/01/2014 3:35:32 PM A exe
WSHost.exe C:\Windows\WinSxS\amd64_microsoft-windows-store-client-ui-wshost_31bf3856ad364e35_6.3.9600.16477_none_044f612c83e1996e 25,304 28/11/2013 2:36:30 AM 15/01/2014 7:22:33 AM 26/01/2014 3:32:16 PM A exe
How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7, or Windows 8.
http://support.microsoft.com/kb/929833
How to analyze the log file entries that the Microsoft Windows Resource Checker (SFC.exe) program generates in Windows Vista
http://support.microsoft.com/kb/928228#appliesto
See "Cannot repair member file file details".
"This entry indicates that the file content does not match the operating system definition for the file. In this situation, the SFC.exe program cannot repair the file."
How to analyze the log file entries that the Microsoft Windows Resource Checker (SFC.exe) program generates in Windows Vista
http://support.microsoft.com/kb/928228#appliesto
See "Step2: If the System File Checker tool cannot repair a file."
Use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7
http://support.microsoft.com/kb/929833
Have a look at these options too.
System Update Readiness Tool fixes Windows Update errors in Windows 8, Windows 7, Windows Vista, Windows Server 2008 R2, and Windows Server 2008
http://support.microsoft.com/kb/947821
For Windows 8 see the paragraph, "Use Deployment Image Servicing and Management to fix Windows Update errors".
"Use Deployment Image Servicing and Management to fix Windows Update errors" is a expandable live link on that article's page.
Use Deployment Image Servicing and Management to fix Windows Update errors
1.Open an elevated command prompt.
Windows 8 – Elevated Command Prompt
http://www.tweakhound.com/2012/11/12/windows-8-elevated-command-prompt/
2.Type the following commands. Press Enter after each command (allow the command to complete, it is a lengthy process, maybe up to an hour) .
DISM.exe /Online /Cleanup-image /Scanhealth
DISM.exe /Online /Cleanup-image /Restorehealth
3.Close the command prompt, and then run Windows Update again.
CheckSUR: System Update Readiness Tool to repair Windows Update
http://www.thewindowsclub.com/checksur-system-update-readiness-tool