The problem seems to persist: with me, it only appeared a few days ago, with a fresh install of Mac Office (I naturally blamed MS for messing up the Word icon).
Then, I installed Picasa for the first time - same fuzzy icon problem. OK, I thought, they are third party apps, might just not be up to it. But then - with today's iTunes update - iTunes has also gone fuzzy.
On my Mac, the effect seems to appear with apps only, and only after updates or fresh installs. I have not found any other files/folders with this effect. Yet.
This is annoying! Neither a finder restart nor deleting the finder preference list have helped so far. I tried CocoThumbX as well to refresh the icons. No result.
This thread is definitely not answered yet.