It appears that the latest security patches from Microsoft, deployed over the last Patch Tuesday, are causing serious problems for some users of their Windows operating systems, including Windows 7.

The affected Windows machines simply stop working and start displaying a (mostly) black screen, in some cases showing only a “My Computer” Explorer window.

The problem was first noticed by UK security company Prevx, which already offers a software fix. The folks at Prevx claim that this is no small matter, and that this “massively debilitating” issue could potentially affect “millions of Windows users.” However, no official fix is yet available from Microsoft.

A Microsoft representative said that “Microsoft is investigating reports that its latest release of security updates is resulting in system issues for some customers. Once we complete our investigation, we will provide detailed guidance on how to prevent or address these issues.”