Make TextArea height adjust to fit content

Question

I'm trying to get my TextArea to resize and fit the content
it contains but for some reason the following code causes it to
become about 3x higher than the text it contains. Can someone point
out what I am doing wrong? Thanks!
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
layout="absolute">
<mx:TextArea width="400">
<mx:text>
this is a test this is a test this is a test this is a test
this is a test
this is a test this is a test this is a test this is a test
this is a test
this is a test this is a test this is a test this is a test
this is a test
this is a test this is a test this is a test this is a test
this is a test
this is a test this is a test this is a test this is a test
this is a test
</mx:text>
<mx:creationComplete>
event.target.height = event.target.textHeight;
</mx:creationComplete>
</mx:TextArea>
</mx:Application>

Answer 1

Hi Zak - thanks -
Actually... I have a "background frame" on the master page; I have added a text frame to one of the pages based on the master.
The text frame containing the text expands just fine, but the "background frame" set on the master doesn't.
Any ideas?
cheers
Andrew