Index: /CKEditor/trunk/CHANGES.html
===================================================================
--- /CKEditor/trunk/CHANGES.html	(revision 3991)
+++ /CKEditor/trunk/CHANGES.html	(revision 3992)
@@ -199,4 +199,5 @@
 			skin was wrapping improperly in some languages.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/4119">#4119</a> : Unable to edit image link with image dialog.</li> 
+		<li><a href="http://dev.fckeditor.net/ticket/4058">#4058</a> : [FF] wysiwyg mode is sometimes not been activated.</li>
 	</ul>
 	<h3>
Index: /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 3991)
+++ /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 3992)
@@ -217,4 +217,5 @@
 						isLoadingData,
 						isPendingFocus,
+						frameLoaded,
 						fireMode;
 
@@ -230,4 +231,5 @@
 							fieldset.remove();
 
+						frameLoaded = 0;
 						// The document domain must be set within the src
 						// attribute;
@@ -263,4 +265,11 @@
 						if ( CKEDITOR.env.gecko )
 						{
+							// Double checking the iframe will be loaded properly(#4058).
+							iframe.on( 'load', function( ev )
+							{
+								ev.removeListener();
+								contentDomReady( iframe.$.contentWindow );
+							} );
+
 							// Accessibility attributes for Firefox.
 							mainElement.setAttributes(
@@ -308,8 +317,4 @@
 							'window.onload = function()' +
 							'{' +
-								// Remove this script from the DOM.
-								'var s = document.getElementById( "cke_actscrpt" );' +
-								's.parentNode.removeChild( s );' +
-
 								// Call the temporary function for the editing
 								// boostrap.
@@ -321,8 +326,17 @@
 					var contentDomReady = function( domWindow )
 					{
-						delete CKEDITOR._[ 'contentDomReady' + editor.name ];
+						if ( frameLoaded )
+							return;
+
+						frameLoaded = 1;
 
 						var domDocument = domWindow.document,
 							body = domDocument.body;
+
+						// Remove this script from the DOM.
+						var script = domDocument.getElementById( "cke_actscrpt" );
+						script.parentNode.removeChild( script );
+
+						delete CKEDITOR._[ 'contentDomReady' + editor.name ];
 
 						body.spellcheck = !editor.config.disableNativeSpellChecker;