What makes this very strange, is the fact that you don't even have "Disable Flash Animations" checked in the tools menu. blocker.swf is basically a blank transparent flash animation file, that is used to replace normal flash animations on sites. The idea behind it, is to replace as little as possible to block animations, to prevent breaking the site. Simple enough...
But for some reason it is trying to actually download the blocker.swf, without Avant even trying to block animations. Furthermore, it's trying to download it from a server on your computer (hence the localhost). The first thing that comes to mind, is that it's either some other third party ad blocker or malware, just for the fact that it is trying to download from a server. But it's still pretty unlikely.
Though, the server thing could be a way to make Avant more compatible with Vista. Simply using something like "file://Program Files/Avant Browser/res/blocker.swf" produces an access denied error in Vista.
I guess you can try checking "Disable Flash Animations", and see if it is functioning properly as a test. If it's not, you can try restoring the default settings for Avant Browser. If that still doesn't fix it, then AVG may be blocking it somehow.
I'm not convinced Outlook has anything to do with it. Unless Outlook is also incorporating some kind of server in itself, which is overriding Avant's server.
If that is the case, I think Avant Browser needs to seperate it's server usage into a port. Example; http://localhost:5278/bloacker.swf
. Not only will it prevent issues like that, it's just better practice.