Yeah Ernie, I have posted about this exact same issue, and found the same results in this thread I created
Mysterious Downloads in 4.0.3 (I didn't know this vague titled thread was dealing with the same bug, otherwise I would have posted of my issue here).
Checking out Outbrain.com, I doubt the downloads are malicious, but just some bug/issue with their particular programing, or way their widget works, with the Safari update... or vice/versa.
But then again, I think this is not just limited to just Outbrain's widget thing, and that other users in this thread have found the issue being occurred by other sources... which again leads me back to my original post in my thread, that this just may be a small issue with Safari 4.0.3 dealing with certain javascript traffic/tracking cookie/widget things.