setTextFormat won't work!

Hi guys,

I’m working around with the text in flash and formatting it through actionscript i used the TextFormat class. I have a button and during roll over event i set my text style to bold. The code is something like this
var txtFormat:TextFormat=new TextFormat();
txtFormat.bold=true;
myTextbox.setTextFormat(txtFormat);

but then some fonts like Arial and Tahoma, the code won’t work but when i use a Lucida Grande font it works fine, but only with ALPHA CHARACTERS.Numbers and special characters are missing…I already embedded all the Characters needed. Do you have any idea regarding this problem guys?

Your post is greatly appreciated.