Microsoft confirmed on Wednesday that rootkit malware is causing "blue screens of death" boot problems for some users who applied a Windows kernel security patch.

The patch, MS10-015, was released last week as part of Microsoft's February security update. The problem wasn't with the patch. Instead, affected systems had Alureon malware that caused restart problems after the patch was applied, explained Microsoft Security Response Center Director Mike Reavey, in a blog post.

"We were able to reach this conclusion after the comprehensive analysis of memory dumps obtained from multiple customer machines and extensive testing against third party applications and software," Reavey wrote. "The restarts are the result of modifications the Alureon rootkit makes to Windows Kernel binaries, which places these systems in an unstable state."

The boot problem happens because the Alureon malware attempts to access a specific memory location rather than allowing Windows to determine it on loading an executable file, Reavey explained.

The malware doesn't affect 64-bit systems, according to Microsoft, but 32-bit systems can be vulnerable. Microsoft suspended the automatic release of security bulletin MS10-015 through Windows Update but expects to resume delivery after further work.

"Microsoft is striving to resolve the issue as quickly as possible, and as such, will continue to hold offering MS10-015 through Automatic Update for 32-bit Windows systems until a solution is available," said Microsoft spokesman Jerry Bryant in an e-mail statement.

At least one software security analyst praised Microsoft for its quick response.

"You have to give credit to Microsoft for quickly recognizing the issue and rushing to fix the issue versus waiting for their monthly cycle," said Chris Merritt, director of solution marketing at software security firm Lumension.