Hi. I have had absolutely the same problem. There were three lines outputting the_date, the_title and the_excerpt in the same loop, and they printed data from different posts.
Also notice that I used WP_USE_THEMES as false, I had my own loop with get_posts command. But I had setup_postdata correctly.
The solution was simple. I didnt declare $post as global. So. don
t forget, this is important.