Images not showing up in Media Library when inserting on Posts page

I’ve been adding images to my posts via the usual Media Uploader. I re-use some of these images, so I’d prefer to only have one copy on my server. When I create a new post and insert an image, I try to find it in the Media Library (while still on the “New Post” screen). No images come up immediately, though I can search and eventually find them, and they’re are there if I actually go to the “Media Library” section of the admin.

Any idea why they wouldn’t load automatically (as happens in other WP installs that I’m working with)?