Activeupdate.com isn't even remotely to do with Microsoft as far as I can tell from the domain information, so it should probably be a restricted site.

Have you run a spyware removal tool yet? I use Spybot Search & Destroy (The home of Spybot-S&D!) which does a good job of detecting threats, informing you of their presence and removing them if deemed appropriate. It could be that you have some sort of software trying to access these sites in order to download updates to the software or whatever and your security is trying to block them.

I've got a handful of blocked sites showing but nothing like the numbers you are reporting.

John