After updating functions.php, all I get is a white screen.

So I am running Thematic PowerBlog on my localhost right now and I’m trying to figure out where I went wrong in my PHP so that I keep getting white screens when I try to update the PHP (such as when I create a new widget area). And then sometimes when I update the PHP I can view the site perfectly well but I can’t log in to the admin panel. I just get a blank white screen.

Here is my PHP code. I’m very new to this so I’ve been learning my trial and error. An extra set of well-trained eyes would be appreciated!

[Code moderated as per the Forum Rules. Please use the pastebin]