Recently, while implementing jQuery Tools’s scrollable, I came across a “jquery.event is not a function” error. I used the un-minified versions of the scrollable jQuery along with its plugins, autoscroll and navigator, in order to troubleshoot, but no matter what I tried, I kept getting this same error. Finally I read on a drupal forum that this error could be caused by an outdated version of jQuery.js. I updated that file, and the error vanished.
The moral of the story: this out of date file could be causing all kinds of mysterious errors, so make sure you have the latest version of jQuery before spending hours troubleshooting all the other files.