internetheaven - 1:41 am on Jan 23, 2013 (gmt 0)
I found the problem. I went to "Tools > Page Info > Media" and the box for "block images from this site" was checked ... why, I don't know.
If anyone has an answer for that, I'd love to hear it! Why would Firefox suddenly decide to start blocking images from a site I've been working on all day?