This is a small issue I seem to run into when I use the Flash CS5 IDE. I'll create a text field at some point in the project only to come back the next day to find that it won't display the text. Only something I can put down to as a glitch in Flash. A simple fix I found today was to move the file and reopen it - and yep.. the fonts come back. No idea why but seems to be an issue a few people have run into, hope this helps some people out.