A few Drupal users noticed that their CKEditor was not working in IE8. They had also noticed that the Debug Bar they had used was showing the error "Line 11 - Error Insufficient memory to continue this operation." The IE8 debugger tool also showed the following errors 'Drupal' is undefined on line 21, 25 and 28 in ckeditor.config.js & "insufficient memory' on line 11 in ckeditor.js". If you are facing the same issue in your Drupal site when using IE8 then read on.