I've tried many different configurations of the sign-up page, and none seem to work. I can add users via the admin panel, and I can send out e-mail, so I think PHPList is installed OK.
Here is a brand-new, unedited sign up page I just created: http://michiganjapan.com/wordpress/lists/?p=subscribe&id=4
Fill it out, press the button, and you are taken to a blank page. No user is added to the list. I've tried fooling around with this thing for hours and hours with now luck...any ideas?