Javascript – CKEditor instance already exists

I am using jquery dialogs to present forms (fetched via AJAX). On some forms I am using a CKEditor for the textareas. The editor displays fine on the first load.

When the user cancels the dialog, I am removing the contents so that they are loaded fresh on a later request. The issue is, once the dialog is reloaded, the CKEditor claims the editor already exists.

uncaught exception: [CKEDITOR.editor] The instance "textarea_name" already exists.

The API includes a method for destroying existing editors, and I have seen people claiming this is a solution:

if (CKEDITOR.instances['textarea_name']) {
CKEDITOR.instances['textarea_name'].destroy();
}
CKEDITOR.replace('textarea_name');

This is not working for me, as I receive a new error instead:

TypeError: Result of expression 'i.contentWindow' [null] is not an object.

This error seems to occur on the "destroy()" rather than the "replace()". Has anyone experienced this and found a different solution?

Is is possible to 're-render' the existing editor, rather than destroying and replacing it?

UPDATED
Here is another question dealing with the same problem, but he has provided a downloadable test case.