For those of you who install fresh WordPress 3.5.1, you may experience some buttons / links of the HTML editor didn’t work such as the toggle between View/Text button, the Add Media or Add Image button. If it behaves so, this is another option you can do to fix it.
1) Back up all your WP files and Database
2) Go to this website http://wordpress.org/download/release-archive/ and download Version 3.4.2.
3) Install on your server.
4) Now log in as WP Admin and upgrade to 3.5.1. It should take care of the issue.

For those who installed customized WP theme, you can re-install the same theme after the upgrade.