In Flex 3, TextArea – you cannot use both embedded fonts vs local fonts in the same text area. It’s either one or the other. Also, there is property that you can use to tell the text area to use embedded fonts. By default, this value is TRUE. In order to access, the property you would need to use the namespace and then can access the property:
this.textField.getTextField().embedFonts = TRUE/FALSE;
Also, beware of global properties that are set in your external CSS file. If you are using a global font and are did not specify a font for the TextArea – IT will use the global font.