The problem was said to stem from an error in the November "Patch Tuesday"
release. Security firm Prevx originally reported that the update was editing
registry keys, potentially causing an error which would leave users with a
completely blank screen.
"We have conducted a comprehensive review of the November Security Updates,
the Windows Malicious Software Removal Tool, and the non-security updates we
released through Windows Update in November," the company said in a blog posting.
"That investigation has shown that none of these updates make any changes to
the permissions in the registry. Thus, we don’t believe the updates are related
to the ‘black screen’ behaviour described in these reports."