I've been using the TweetDeck app and the stock black icon sorta melts into my "Black Shelf" dock. I found a couple of icons to change it into something different, only one problem... it wont let me! Originally I was opening the "get info" and copy/pasting the images If that failed, I was using img2icn and that worked out. But this wont let me change anything! Even when I've unlocked it! Any ideas?