IE 8-9 source button not work

Hi ,

I use ck editor 4.1 and in IE 8,9 when I click on source button , I can't click back .

In FF it works correctly .

Any idea ? any workaround ?

Thx

//EDIT:

I debug it little bit , and when I click on source button I got errro

SCRIPT5007: Unable to get value of the property 'on': object is null or undefined
plugin.js, line 131 character 4

in plugin.js for plugin stat on bold line

var startSelect = false;
        editor.on( 'mode', function( e ){
            if ( editor.mode != 'source' )
                return;
            editor.textarea.on( 'keyup',keyDownEvent);
            editor.textarea.on('mousedown',function(e){
                startSelect = true;
            });
        });