Microsoft on Tuesday denied a claim that its November security patch is among the possible causes of the black screen problems affecting some Windows users.

On Friday, Prevx, a maker of antivirus software, attributed some of these black screen crashes to a recent Window operating system change that locked down Windows registry keys.

But Microsoft insists that's just wrong.

"Microsoft has investigated reports that its November security updates made changes to permissions in the registry that that are resulting in system issues for some customers," said Christopher Budd, Microsoft security response communications lead, in an e-mailed statement. "The company has found those reports to be inaccurate and our comprehensive investigation has shown that none of the recently released updates are related to the behavior described in the reports. While we were not contacted by the organization [that] originally made these reports, we have proactively contacted them with our findings."

Budd said that Prevx's claims do not match known issues documented in security bulletins or Knowledge Base articles.

A spokesperson for Prevx, which is based in the U.K., did not immediately respond to a request for comment.

Delving into the issue in greater detail in a blog post, Budd also disputes Prevx's claim that the black screen issue represents a widespread problem.

Prevx's Dave Kennerley in a blog post suggested that millions of computers running Windows have been having black screen problems.

Microsoft's Budd counters that his company's worldwide Customer Service and Support organization is "not seeing 'black screen' behavior as a broad customer issue."

He adds that seeing a black screen is a known symptom of certain malware families, such as Daonol.

Update: In a blog post published shortly after this story was filed, Prevx's Jacques Erasmus confirmed that Microsoft's patch was not to blame and apologized to Microsoft "for any inconvenience our blog may have caused."

The black screen problem appears to be linked to improper alteration of the Shell value in the Windows registry, as explained in the blog post.

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