SVCHOST.exe and Windows updates are 2006ish problem is back again. SVCHOST.exe hogs around 50% of your CPU power and a lot of memory if you go to your task manager or (process explorer - a better program by Mark).
Basically users with CA Antivirus are affected by this problem.
A temporary fix to this solution is to:
Disable Automatic Updates
OR
Disable CA Realtime Antivirus scanner
OR
Prevent CA Antivirus to scan *.msi and *.msp files.
The above workaround should definitely fix SVCHOST.exe problems.