How to solve this sort of problem:
First, clear your browser caches. You want to make sure that the browser is indeed downloading all the javascripts and such and not trying to use old versions.
Second, if it’s still not working after a full clear and refresh, then check the Javascript console for errors. This will tell you what sort of problem you’re having.
A 403 forbidden means that your browser isn’t able to load the scripts up because your server isn’t allowing it. Unfortunately, this is a hard one to solve. Anything could be blocking the server. Check your .htaccess files for anything strange, and/or ask your host what’s going on. Also try a full manual upgrade, to make sure all the WordPress files are there and correct.
If you can actually load those links in your browser, then you should see all the code and that means that you should be fine.
Any “not defined” messages mean that your browser is not loading all the scripts. Same basic problem, the trick is just to figure out why.