Calendar Links to “%pos” — Returns 404 Err

My calendar is not working. I am using WordPress 1.2. It updates, and shows days with posts, and the title attribute contains the post titles for that day, but clicking on a date links to “http://www.wallofsleep.com/wordpress/%pos” (which always returns a 404 error). The code in my index.php is:
<?php get_calendar(); ?>
I have my permalinks set to /%postname%.htm and my .htaccess set to the recommended values.
Any ideas? Thanks.