Javascript makes Admin theme disappear

I have just added the cufon moduel to my site, and once the http://cufon.shoqolate.com/js/cufon-yui.js was added to the module directory the Slate theme stopped working, I have seen comments relating to a javascript conflict floating around the web but nothing I could really make sense of.

Any help much appreciated as this may help with a similar bug I have on a client site as well as my own.

btw I am using Firefox 3.0.13, Mac OSX 10.5.8 and Drupal 6.13