Index: /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js
===================================================================
--- /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 3672)
+++ /CKEditor/trunk/_source/plugins/wysiwygarea/plugin.js	(revision 3673)
@@ -164,7 +164,9 @@
 				nextElement = fixedBlock.getNext( true ),
 				enterBlock;
-			if ( !previousElement.is( nonExitableElementNames ) )
+			if ( previousElement && previousElement.getName
+				 && !( previousElement.getName() in nonExitableElementNames ) )
 				enterBlock = previousElement;
-			else if ( !nextElement.is ( nonExitableElementNames ) )
+			else if ( nextElement && nextElement.getName
+					  && !( nextElement.getName() in nonExitableElementNames ) )
 				enterBlock = nextElement;