After running the most recent Update for Windows Vista (Home Premium- 64 bit) I evidenced a noticable "hiccup" or freeze occuring occasionally during flash games and other relatively simple graphics tasks (which my computer had never had before, and certainly shouldn't show for such low-powered applications.)
The only things I installed during the update were the latest files for Windows Defender and the ActiveX Killbits patch.
I've since done a Windows Restore/Rollback; hopefully that will be the last I see of it. This is one part warning, one part curiousity if anyone else has noticed anything similar. Though I realize there are so many dang flavors of Windows Vista, on so many different kinds of hardware, that it's entirely possible I'm the only one here who's seen this.
ADD: Looking at what Vista wants to install now, post-rollback, I may have been mistaken. The ".NET framework Service Pack 1" (etc.) is part of the update, and I'm going to hazzard a guess that that's the more likely candidate for causing my stuttering.