http://support.microsoft.com/kb/932494
FIX: When you run Windows Update to scan for updates that use Windows Installer, including Office updates, CPU utilization may reach 100 percent for prolonged periods
SYMPTOMS
You use Automatic Updates (Svchost.exe) to scan for updates or to apply updates to any applications that use Microsoft Windows Installer 3.1. Then, you experience issues when you use the following update mechanisms:
• Microsoft Update
• Windows Server Update Services (WSUS)
• The Microsoft Baseline Security Analyzer (MBSA) 2.0
• Microsoft Systems Management Server Inventory Tool for Microsoft Updates (SMS ITMU)
Some of the applications that use Windows Installer include Microsoft Office 2003, Microsoft Office XP, and Microsoft Windows Defender. These applications experience the following issues:
• The Svchost.exe process may spike the CPU usage to 100 percent during update detection or update installation. Also, the Svchost.exe process causes the computer to stop responding for various lengths of time.
• The Svchost.exe process produces an access violation during update detection or update installation. Additionally, you receive the following error message:
SVCHOST.exe Application Error
The instruction at 0x0745F2780 referenced memory at 0x000000000 the memory could not be read.
• The Svchost.exe process leaks memory during update detection or update installation.
Microsoft has released a hotfix to correct the problem. You can find the hotfix here:
http://support.microsoft.com/kb/927891/
This update replaces update 916089, the orignal fix which is noted in the KB932494.
(http://support.microsoft.com/kb/916089/) When you run Windows Update to scan for updates that use Windows Installer, including Office updates, CPU utilization may reach 100 percent for prolonged periods.