Media uploader missing after 2.7.1 upgrade

After a lot of trouble with the automatic upgrade, and a lot of mucking about with permissions (it got stuck on any file with 644 and wanted it to be 666), I finally gave up and upgraded manually. Now I don’t have any of the Media Uploader icons above the Write Post box. I suspect one or more files don’t have permissions set correctly. I have set directories to 755. Can anyone tell me which files control the Media Uploader buttons, and what permissions they should be set to?

I can access the Media Library from the sidebar and the Add New link is there as well. But no buttons above where you write your posts.