Microsoft Security Advisory KB927891 - fix for Windows Installer (MSI) problems
Symptoms:
Your system may appear to become unresponsive when Windows Update or Microsoft Update is scanning for updates that use Windows installer, and you may notice that the CPU usage for the svchost process is showing 100%.
When you try to install an update from Windows Update or from Microsoft Update, you experience the following symptoms:
• Your system may appear to become unresponsive when Windows Update or Microsoft Update is scanning for updates that use Windows Installer.
• You receive an access violation error in svchost.exe. This access violation stops the Server service and the Workstation service.
• A memory leak occurs when Windows Update or Microsoft Update is scanning for updates that use Windows Installer.
• Windows Update or Microsoft Update scans take a very long time, sometimes hours, to complete.
The fix is now available on WSUS and via Windows/Microsoft Update, and will require a restart after installation.
Source: http://www.microsoft.com/technet/security/advisory/927891.mspx
Associated KB - http://support.microsoft.com/kb/927891