I have the same exact issue with a huge glossary post, but I figured out a workaround:
Using phpmyadmin to edit the post_content field under the wp_posts entry for your post you can paste in your html and it updates the blog entry without using wordpress. This works, which says three things: the issue is not a mysql, php, or server configuration problem– it’s wordpress.
It’s mostly simple if you have phpmyadmin, know how to use it, and don’t ever need to conveniently update your post.
