A common source for this problem is the use of the applet caching mechanism in conjunction with the JavaScript API for Mac OS. For technical reasons, the Mac OS JavaScript API does not work when the permanent caching of the editor is activated. Please make sure that none of the following parameters are included within your applet tag:

        <param name="cache_archive" value="edit-on-pro-signed.jar ">
        <param name="cache_version" value="...">
        <param name="cache_option" value="plugin">

Those parameters only need to be disabled on Mac OS X. In general they can be used on all other platforms. After removing those parameters, clear your browser cache, then reload the applet. Now the Mac OS X JavaScript API should work properly.