I was fiddling with functions.php this morning, and a little bit later I noticed that all my links were going to blank pages. Even within the admin panel, when I updated a page, it kept going to blank pages.
Searching the WP forums was frustrating, so I wanted to share the solution to my problem.
The only thing I needed to do was to go back to functions.php and remove ALL blank lines. Apparently if there are any empty lines, there's trouble. I actually ran into this problem a long time ago after an upgrade as well, so even if you didn't edit the file yourself, this could be the issue. Going back and making sure there were no blank lines solved it both times.
I hope this helps someone in the future!