strange reply text formt

Recently when I reply to plain text e-mails in Outlook 2003 (Windows XP) the
format of the reply is in very tiny italics. Since it is plain text format,
all the font choices are grayed out--I can't simply click on the italic
button to change it. Although the toolbar says "courier new 10 -italic" and
the zoom is at 100% (so it's not an issue of the scroll wheel on the mouse),
the appearance of the text is much smaller than 10-point and barely readable.
This just started happening recently. How do I undo this, so that the reply
appears similar to the received message? Thanks in advance.