Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 5394)
+++ /CKEditor/trunk/CHANGES.html	(revision 5395)
@@ -151,4 +151,5 @@
 		<li><a href="http://dev.fckeditor.net/ticket/5416">#5416</a> : [IE] Delete table throws a error when  CKEDITOR.enterMode = CKEDITOR.ENTER_BR.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/4459">#4459</a> : [IE] Select element is penetrating the maximized editor in IE6.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/5559">#5559</a> : [IE] The first call of CKEDITOR.editor::setData is affected by iframe cache when loading wysiwyg mode.</li>
 		<li>Updated the following language files:<ul>
 			<li><a href="http://dev.fckeditor.net/ticket/5326">#5326</a> : Catalan;</li>
Index: /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 5394)
+++ /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 5395)
@@ -290,5 +290,4 @@
 							iframe.remove();
 
-						frameLoaded = 0;
 
 						var setDataFn = !CKEDITOR.env.gecko && CKEDITOR.tools.addFunction( function( doc )
@@ -304,6 +303,4 @@
 							// call document.open().
 							( isCustomDomain ? ( 'document.domain="' + document.domain + '";' ) : '' ) +
-
-							( ( 'parent.CKEDITOR.tools.callFunction(' + setDataFn + ',document);' ) ) +
 
 							'document.close();';
@@ -313,7 +310,8 @@
   							' frameBorder="0"' +
   							' title="' + frameLabel + '"' +
-							// With FF, the 'src' attribute should be left empty to
+							// With IE, the custom domain has to be taken care at first,
+							// for other browers, the 'src' attribute should be left empty to
 							// trigger iframe's 'load' event.
-  							' src="' + ( CKEDITOR.env.gecko ? '' : 'javascript:void(function(){' + encodeURIComponent( srcScript ) + '}())' ) + '"' +
+  							' src="' + ( CKEDITOR.env.ie ? 'javascript:void(function(){' + encodeURIComponent( srcScript ) + '}())' : '' ) + '"' +
 							' tabIndex="' + editor.tabIndex + '"' +
   							' allowTransparency="true"' +
@@ -321,6 +319,7 @@
 
 						// With FF, it's better to load the data on iframe.load. (#3894,#4058)
-						CKEDITOR.env.gecko && iframe.on( 'load', function( ev )
-							{
+						iframe.on( 'load', function( ev )
+							{
+								frameLoaded = 1;
 								ev.removeListener();
 
@@ -346,7 +345,7 @@
 					var contentDomReady = function( domWindow )
 					{
-						if ( frameLoaded )
+						if ( !frameLoaded )
 							return;
-						frameLoaded = 1;
+						frameLoaded = 0;
 
 						editor.fire( 'ariaWidget', iframe );