TextField not showing line breaks

This is really weird, I have a dynamic text field with embedded fonts on the stage, with some paragraphs of text in it, I pushed enter a few times, so theres some line breaks in it…

If i test the swf, the text displays correctly. But, if i turn on bold or italic, the line breaks vanish.

So instead of

Line one

Line two

I get

Line one
Line two

What on earth is going on? This happens with normal fonts like Arial…