Original URL: http://www.theregister.co.uk/2009/11/30/prevx_microsoft_black_screen/

Prevx blames Microsoft for black hawk screen down

Patches bestow chocolate teapot status on Windows PCs

By Kelly Fiveash

Posted in Operating Systems, 30th November 2009 13:50 GMT

Microsoft’s most recent release of security patches is causing some computers to freeze and display a, er, black screen of death.

The glitch is affecting Windows 7, Vista and XP operating systems, according to software security firm Prevx.

The UK-based company warned its users on Friday that Microsoft’s latest patches were causing havoc for some Windows fans.

According to a blog post by Prevx late last week, Redmond tweaked the Access Control List (ACL), which among other things details individual object permissions for a logged-on user within the Windows file system.

Microsoft’s latest modification to ACL registry keys have rendered some installed apps as useless, by preventing them from running and causing a black screen to appear.

Prevx noted that security apps were particularly badly affected by the patches, and added that some users of Prevx’s products had attempted to reinstall their operating system in a desperate effort to resolve the problem.

Prevx has already spun out a fix for users affected by the problem that automatically matches its software to the registry tweak in order to align with the ACL settings.

"I must stress that this tool will not fix all black screen issues," said Prevx support wonk Dave Kennerley.

"There can be many causes. But if your black screen woes began in the last two weeks after a Windows update or after running any security program (including Prevx) to remove malware during this time then this fix will have a high probability of working."

Kennerley added that Microsoft had failed to adequately alert the developer community about the rule changes it had made to the ACL with its latest patch batch, which was released on 10 November. ®