Thread:Project:Support desk/Image upload freezes

I can't get image uploading to work. When I click the "Upload File", the browser just gets stuck loading, with nothing ever appearing. (This is different than getting a blank result -- it's stuck waiting for a result.)

To help debug, I've created a fresh, vanilla MediaWiki install. I went through the config process and then modified LocalSettings.php with "$wgEnableUploads = true". I can login as admin and create pages just fine, but the upload page still freezes.

Things I've checked:
 * Permissions. The images directory is readable/writeable by everyone (insecure, I know, but I'll address that later).
 * PHP. Seems to be properly configured: "file_uploads = On"; "open_basedir" is not set.
 * ImageMagick. Logging calls to "convert", it appears this never gets called.  Just in case, I also tried turning off wgUseImageMagick.  Didn't matter.

Any ideas? At the very least, how do I go about diagnosing the problem?

Versions: MediaWiki 1.16.5, PHP 5.3.4, MySQL 5.1.44, OS X 10.6.7