Can’t execute PHP in post/pages WITH Exec-PHP

Hey guys, my wordpress is located at http://lifeaspaul.com, and I’m trying to enable it so that I can use PHP code in a post/page (to display hit counter stats on a page). Anyways, I have installed Exec PHP v4.4, and the plugin installed correctly and is enabled in my plugins menu, but I am still unable to use PHP in my posts/pages. I’m running WP v2.3.3.

Here’s all I’m trying to do:
<?php echo counterize_getuniqueurl() ?>

And when I save the post and come back to edit it, this is what I get in the VISUAL write tab:
< ?php echo counterize_getuniqueurl() ?>
And this is what I get in the CODE write tab:
&lt(;) ?php echo counterize_getuniqueurl() ?&gt(;)
(the < and > have been parsed into the code, &lt and &gt)

Can anyone tell me how I can enable PHP in my posts and pages please?