I recently received a Flash file that another artist had worked on many months ago. When I tried to insert a new text box with new copy, I found that the text (Ariel Regular, 11pt) was actually displayed much smaller that it should have. I copied and pasted a text box from another Flash file (Same font and pt size) and it came in at the proper size. But any new text boxes created in the file display much smaller text.
It could be embedded in a movieclip that is being scaled down. Meaning, if you are pasting the text into a movieclip living on the stage, and that movieclip has been changed from native size, it will scale the text as well.