Some folks who installed the MS10-015 security patch from Microsoft were left with the dreaded blue screen of death (BSOD) that prevented those PCs from booting up. Turns out, this might be the best thing that could have happened to those users - the BSOD resulting from MS10-015 has been traced to infections by the rootkit-enabled TDSS malware. Microsoft isn't ruling out other possible causes; however, if you've experienced the blue screen of death after installing the February security patches from Microsoft (in particular, MS10-015) it's a good idea to take this as a sign that your computer is very likely trojan-infested.
Of course, many folks that were affected may not even realize there was a security patch at the root of it all. If you have automatic updates enabled, the MS10-015 patch would have been installed automatically in the second week of February. If you've been struggling with blue screens since then and unable to boot your computer, it's a pretty safe bet it was from that patch (and the presence of the TDSS rootkit).
If you or someone you know are experiencing the blue screen of death after having installed MS10-015, you can get help by visiting consumersecuritysupport.microsoft.com or by calling 1-866-PCSafety (1-866-727-2338). (International users can find support contact numbers at http://support.microsoft.com/common/international.aspx.)