Cannot Edit Existing Posts in WP 2.0

I am having a problem where I cannot successfully edit my existing posts.

I create a post and publish it. Then when I try to edit the same post something strange happens. I make my edits and then select Save and Continue Editing or Save. After the save, the contents of the original post are shown in the Title and Post contents of the Write Post section; however, the Post Preview section has the updated content (the original plus the edits). View the post shows the updated contents.

I had WP 1.5.2 running on my setup for months without this problem.

– meb

Setup Info: IE 6 SP2 is my browser; IIS 5/PHP 4.38/MySQL 3.23.49