Note that you can't install KB3161647 by itself; it has to be installed with the update rollup KB3161608.

You'd have to install KB3020369 first and then KB3161608. KB3020369 had its own share of issues.

There are also other possible fixes:
http://www.infoworld.com/article/308...ate-scans.html
The monthly Win7 patch whack-a-mole has been reaching Keystone Kops proportions. In April, poster EP on AskWoody.com discovered that installing two completely unrelated patches -- KB 3138612 and KB 3145739 -- could reduce Win7 update scan times from hours down to minutes. In May, EP found that installing a totally different patch, KB 3153199, also did the trick. In June, the magic bullet came from KB 3161664. All of these solutions had one thing in common: they involved replacing win32k.sys. Apart from that, they seemed to be completely random.
I prefer to do offline installs anyway. You can try Autopatcher.
http://www.autopatcher.net/forum/viewforum.php?f=3