This is the latest update designed to address the DNS vulnerability that has been widely reported in recent days.
Unfortunately, for me it seems that installing this update essentially stops my Netvigator connectivity from working (not entirely, but almost - I might get one page down after a full reset but then nothing).
I've uninstalled it from my machines at home and everything is fine again.
Is anyone else having the same problem or is it something specific to my setup (two XP SP2 machines running through a Linksys WRT54G wireless router)?