A movie whether Flash or Quicktime uses a plug in to display on your page and because of this it floats to the top obscuring a text layer you may try and put over it.
The only reliable way to get this to work is to put the text into the movie.
You could try extending the attributes of the movie by selecting the movie container Item>Extended click on the Embed Tab and create a new name/value pair of wmode/ transparent but you will probably get varying results in different browsers.
Also add z-index 99 using the same method to your text layer.
Have you a link you can share with us so that we can see what is there already?