Windows Update site was slowed by heavy traffic last month following the release of four Microsoft security updates fixing critical holes in Windows software. Saturday's Sasser worm used one of those flaws, a buffer overflow in the LSASS Windows networking service, to compromise unpatched machines. It's not yet clear whether today's delays are due to increased patching by tardy network administrators, or some other cause. Microsoft said it addressed last month's performance problems by "adding resources to support Windows Update."
Dynamically updating performance charts for Windows Update are available here.