For some reasons if windows 8 fails to install updates properly it start rolling back changes and it try to recover from that update , it cause of problem at every reboot .
To fix errors that occur when you use Windows Update, install and run the System Update Readiness Tool. The tool scans for inconsistencies on your computer and fixes them as it’s being installed.
to fix that :
- Open CMD as administrator
- DISM.exe /Online /Cleanup-image /Scanhealth
- DISM.exe /Online /Cleanup-image /Restorehealth
after that run windows update again
Microsoft KB : http://support.microsoft.com/kb/947821