I have a similar issue: I need to set the text of the editor on window load, on the client side.

I used

function window.onload()

{

     var editor1=document.getElementById('<%=Editor1.ClientID%>');
     var editdoc=editor1.GetDocument(); 
    editdoc.body.innerHTML=unescape('some text');

}

 

I noticed that this method actually gets called, but something else ERASES this text afterwards. So I used window.onfocus() instead, and it works.

However, for my case, onfocus is not good enough and it doesnt fire always.