about setData

This is the first time that I am using CKeditor on my website. Basically what I want to do is have a javascript event clear the content of the editor, then insert a certain message into it.

I assume that I can use setData to clear the content of my editor:
CKEDITOR.instances.editor.setData(' ');

Then I want to insert a message:
CKEDITOR.instances.editor.insertText( 'adfadsf' );

The content is cleared, but the message is not inserted into the editor, and Firebug gives me this error:
D.getStartElement() is null, of which I cannot make heads or tails... Please help! Thanks in advance!