The problem began with upgrade to 3.3 and continues after upgrade to 3.3.1
Media upload screen comes up - still old design (not the new drag and drop interface) clicking "Select" in flash uploader is unresponsive. Clicking "Browser Uploader" is also completely unresponsive.
I've tried everything on the master list: flushed cache in 2 browsers, deactivated all plugins, twenty-eleven theme and a manual upgrade ... nothing helps.
I don't know of this has anything to do with the problem but Firebug net view shows a recurring 404 error in accessing: