Ajax captcha reload not working

I have a script that outputs a random captcha and session keystring. I
am trying to create an AJAX reload link that will regenerate the image
when a user can't read it properly. The problem is the AJAX function
keeps returning the same image/key that was generated during the
initial page load? If I just visit the actual script url it
automatically changes every time I press reload, so why Is it not
changing when I open the url via AJAX?

Nevermind, I managed to get the same effect using an IFRAME... and
reloading the page dynamically...