I'm running OS X 10.6.7 and Firefox 4.0 (the release version, not beta). Sometimes, when I hit an upload button and browse for files, the dock disappears. When I close the upload window, the dock comes back again. It's happened a few times now. I've already rebooted and done a permissions repair to no avail. Any help? Is this just a bug in OS X or Firefox I need to wait to be fixed?