Hi
I had the same problem a while back with a post about 13,000 words long.
I still have not fixed the problem, but got around it by first creating the post (only about 5000words) and pictures in WordPress so a basic post was in existance. I then edited the database entry via PhpMyadmin of that post and cut and pasted the entire 13,000 words in.
It now appears. Not a solution though.
Any wordpress experts out there have an idea?