I was having a site build in WordPress. I tried to upgrade it from 2.8 to 3.3.2, after upgrading it all the JavaScript in WordPress admin panel stopped working but front-end was working fine.

So I just disabled all the plugins and upgraded the WordPress from 3.3.2 to 3.4.1 version and the admin panel start working again normally and then reactivated all the plugins. Now my site is fully functioning.

NOTE: Do Remember to disable all the plugins before upgrading WordPress.