Ever since changing web hosts, I'd noticed that the image uploader was no longer working properly. Every time I tried to upload an image, everything went fine except for, apparently, the actual upload. Going to the /wp-content/... URL resulted in a 404. I had to upload images manually through my FTP client.
Then, today, I noticed something odd: a /public_html/ folder in my server root. I took a look there, and found a wp-content folder, full of all my lost uploads from the past few months.
The problem is that my old host called the document root of my site /public_html/, while the new host calls it /plankhead.com/. WordPress, for some reason, still seems to think it should be uploading to /public_html/. How can I change this?