I just ran into an issue while migrating an app from Flex 3.5 to Flex 4.1.  I noticed that screens using mx:Text to display htmlText were blank.  Baffled, I performed the old trusty google search.  And found here and here that Flex 4 uses a new standard for font embedding.  The long and short of it, if you use spark components use an embedded font with a embedAsCFF:true; otherwise, Flex 3 MX components should use embedAsCFF:false;


@font-face {
src:url("../assets/fonts/Copperplate.dfont");
fontFamily: myCopperPlate;
font-weight:normal;
}
@font-face {
src:url("../assets/fonts/Copperplate.ttc");
fontFamily: myCopperPlate3;
font-weight:normal;
embedAsCFF: false;
}