Ok, I think I know what is going on, I just can't easily explain it. I CAN, however, walk you through the posting. Follow these steps.

1. Enter whatever text you want in the post that will contain the video.
2. Select "Preview".
3. Make sure that the text is as you want it.
4. Scroll down until you see the editing window.
   
5. Select the purple 'disable rich-text' link found directly under the editing window. Your text will look strange, with a lot of odd characters such as <p> and <a> etc., and all formatting will seem to disappear. Don't worry about it, it should show up fine when it posts.
6. Enter the video code either above or below the text you already entered.
7. Select "Submit".

Do NOT select preview again. Even though the video will appear in the preview, for some reason it will not post. I think it has something to do with the fact that the rich text option turns back on after you preview the post and it wipes out the code. Not sure, however.

Note: if you paste the code above the text, the text will probably form around the video to the left. If you don't want that, try posting the code after the text.

Hope this helps!

Trish