Index: _source/plugins/sourcearea/plugin.js
===================================================================
--- _source/plugins/sourcearea/plugin.js	(revision 4206)
+++ _source/plugins/sourcearea/plugin.js	(working copy)
@@ -64,6 +64,11 @@
 											textarea.show();
 										};
 									editor.on( 'resize', onResize );
+									editor.on( 'afterCommandExec', function( event )
+									{
+										if ( event.data.name == 'toolbarCollapse' )
+											onResize();
+									});
 									styles.height = holderElement.$.clientHeight + 'px';
 								}
 							}
Index: CHANGES.html
===================================================================
--- CHANGES.html	(revision 4206)
+++ CHANGES.html	(working copy)
@@ -64,6 +64,7 @@
 		<li><a href="http://dev.fckeditor.net/ticket/3568">#3568</a> : Dialogs now select all text when tabbing to text inputs.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/3727">#3727</a> : Cell Properties dialog was missing color selection option.</li>
 		<li><a href="http://dev.fckeditor.net/ticket/3517">#3517</a> : Fixed "Match cyclic" field in Find & Replace dialog.</li>
+		<li><a href="http://dev.fckeditor.net/ticket/4203">#4203</a> : In IE quirksmode + toolbar collapsed + source mode editing block height was incorrect.</li>
 	</ul>
 	<h3>
 		CKEditor 3.0</h3>