Thank you. I just experienced this problem and this was the answer for me as well.
However, my first attempt at fixing the problem by saving my content as text and then replacing the page content in admin failed. Hmmmm.....
So, I cut the content from the page and published the blank page. This attempt failed again. The <!--[endif]--> was STILL there in IE!
Then I'm thinking, okaaaay...., I'm seeing it in IE but not in Firefox, let's bring up WP admin in IE. When I looked at the pages, the code was there! So, for the third time, I cut and pasted the entire text version of the content. This got rid of the <!--[endif]--> but the text formatting was all messed up
in IE. It was still fine in Firefox.
So, I checked another page in IE WP admin and, for the fourth attempt, simply deleted the <!--[endif]--> without replacing the content and republished. SUCCESS!!!!! The <!--[endif]--> code was gone and the text formatting retained integrity in both browsers.
Why? Because I tried to do the editing in Firefox and the problem only existed in IE. When you look at the page content in Firefox
WP admin the <!--[endif]--> is not there so it can't be edited out. When you view the page content in IE
WP admin the <!--[endif]--> is there, so it can
be edited out. You DO NOT
have to repaste the entire content.
So, to resolve this problem you MUST view and edit the page content in WP admin using IE. To edit, simply select and cut <!--[endif]--> from the page and republish. The visual appearance of both pages will retain integrity.
However, it's a good idea to check your pages anyway for any stray code which affects the formatting. I have found occasional stray snippets which over ride the Atahualpa settings.
You can mark thread as resolved now?
Good luck and happy authoring.