Time to try something else. We use a variable in the code called "sticky_url", it is the currently loaded url with all the arguments. We determine this from the PHP $_SERVER array. I need to see what your setup is supplying for this array. If you could add the following code to hastymail2/lib/misc_functions.php after line 1069 (current SVN version):

 echo_r($_SERVER);

Then load the message that gives you a page not found message. You will see a bunch of debug information about your server setup above the display. If you could send that to me in an email (don't post it to the forums since it has sensitive info) I can debug this further. You can send it to jason@hastymail.org

Thanks,
Jason