Unable to add new content to a page in IE8 using the WYSIWYG editor after adding a macro

Steps to reproduce:

• Create a new page
• Hover over Edit and click on WYSIWYG
• Click on Macro -> Insert Macro
• Choose any macro and then click "Select"
• Fill in the required fields
• Click "Insert Macro"

You are unable to add new content to the page from the WYSIWYG editor. As a workaround you can switch to the "Source" tab and add new content there. If you save the page and then edit it again in the WYSIWYG editor you still can't add new content.

Doesn't reproduce on Chrome 23, Firefox 17 and IE9.