Internet Explorer problem

Hi, I have Drupal 6.17 and Footnotes 6.x-2.5 installed and working perfectly with CKEditor 6.x-1.1 (3.3), using the method described here - http://drupal.org/node/1152264.

Everything seemed fine, footnotes insert and edit perfectly, apart from in Internet Explorer 8 and 9 when I get '[object Object]' appearing in the dialogue and the 'ok' button doesn't work (cancel does).
Any ideas? And thanks for any help!