[IE8] Undo results in wrong cursor with HTML comment

[Garry Yao]

1. Load the editor with following content and selection:

   <!-- A comment -->
   <p>^foo</p>
   

2. Type some random chars;
3. Click on Undo button;

• Expected: Inserted chars are removed, with cursor restored to the start;
• Actual： Inserted chars are removed, but cursor is now at the end of content.

[Garry Yao]

IE9 and other browsers work well.

[Jakub Ś]

File 2012-04-19_1017.swf shows how to reproduce.

Not only cursor is moved to the end of document but also HTML comments get removed.

Reproducible in IE6-8 from CKEditor 3.0.

[Jakub Ś]

I wasn't able to reproduce this problem in latest CKEditor 4.1.1.