High CPU Utilization on WSUS Clients
Clients who uses WSUS may have noticed that when the client checks for updates the CPU climbs to 100% utilization and the computer becomes unresponsive. Microsoft released a two-tier fix for this.
First, install the hotfix listed in KB927891. There are specific versions for x86, x64 and Itanium platforms, as well as Server 2003 and XP.
Next, install the new WSUS 3.0 Agent software. This new agent will work with WSUS 2.0 or 3.0 servers.
After you install the new software you will still see the CPU peg at ~100% while the client checks for updates, but the computer will still be responsive. This is the result of "deep architectural performance optimizations" in the client software. My testing has shown substantial improvements in performance and shorter update times.