Hi!
It would be super if you could show an image of this situation, but if not, I think there should be no problem with a dynamic text box. Is your background transparent? if so, the back of the textbox (white) could be being "transparentized", but if not, it could be some other item or issue. I would assure you though that if you test a simple Flash movie with a dynamic text box as the main movie, you shouldn't have any troubles with having that has a projector. Checkout some of the samples at:
http://www.swfkit.com/swfkit/samples.html
...like the Notepad example which features a dynamic input box (the area where you type):
http://www.swfkit.com/swfkit/samples...m.html#notepad