The patch is for a particularly critical vulnerability of which experts have begun to see exploits in the last few days.
The knowledge base article goes by the unusually long name: "Your computer stops responding, you cannot log on to Windows, or your CPU usage for the System process approaches 100 percent after you install the security update that is described in Microsoft Security Bulletin MS04-011."
The problem occurs, according to the article, because Windows tries repeatedly to load drivers that fail to load. Microsoft acknowledges that the problem is a bug in the patch and that the company is investigating solutions.
The article also gives one specific example, where the Nortel Networks VPN client is installed and the IPSec Policy Agent is set to Manual or Automatic for the startup type. In such cases, the article suggests disabling the IPSec Policy Agent.
But the problem is a more general one, and these specific drivers need not be involved.
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