see this article/blog.
Microsoft halts Windows Update distribution of security fix after blue-screen reports | All about Microsoft | ZDNet.com
Also for Windows 7:
Extract :
On a related note, I asked Microsoft today whether the company had any new information or update for those users who’ve reported various Windows 7 startup and shutdown problems which some believe are the result of a reliability update that Microsoft pushed to Windows 7 users in late January. A Microsoft spokesperson said Microsoft had nothing new to say about the matter, other than the company would continue to monitor the situation.