No need to send the source to me, just trying to get a better idea what you need from this Div so i can offer some better suggestions.
Let see if i am understanding you right:
<div>some text to start with</div>
Then from there you are us JS to add words/letters one @ a time:
<div>some text to start with <span>this is the added text</span></div>
But because the text is being added one letter @ a time its appears distorted until its all displayed?
Assuming i am on the right track:
it sounds like you're in need of a min-width attribute. the problem is IE does not play nice when it comes to min width.
i dont think this is exactly what your looking for but would this not work:
This is text already in the div
<span>this is where you add text</span>
*keep in mind the only thing separating a div from a span is "display:block" <- add that to a span and it will behave like a div (inline VS block)