I have the following JS code to set the editor contents:

 

var editor1 = obj_Editor1;

editor1.setHTML("Hello");

 

 

When I run this in IE, I briefly see 'Hello' in the editor.  Then after a second the content goes blank. 

 

Here's the initial editor:

 

 

and 1 second later after it 'flashes':

 

 

The editor displays properly in FF.