I’ve been getting the same thing ever since I upgraded to WP 3.1.2 several days ago. I have a lot of images to sort through and the search feature for the media library has become more of a necessity than a luxury.
I am also having the problem, although I haven’t tried deactivating all my plugins yet. I just upgraded to 3.0 a few days ago, and I checked the forum for my theme but there has yet to be a complaint posted to the theme creator for this problem. My theme is pretty complicated — I’m concerned for how much work might be involved reactivating it should I try switching to the default theme. Is that a valid concern?
I’m having the same problem.