A couple of questions before i can investigate:
1. Which version of Flash Authoring are you using? and You are trying to publish it as a png (i guess) ?
2. What kind of text field have you created ? e.g . Static Text? dynamic Text, TLF Text
3. Did you create the text field from AS ? or during design time?
4. Have you embedded the font for the text ?
Can you share the content ? using may be google docs?
Just to give you a suggestion, try changing the text to Static text with embedded fonts and see if that works for you.
Check your text field is visible on first frame, Since whatever you see on first frame that only can export to image.
Atleast in CS5, you can click on the frame in the timeline that needs to be published as png and then publish (using the publish settings), the current frame in the timeline that has been selected will be exported.