I doubt you still need this, but since I had the same problem and solved it myself, here it goes:
Although you are seeing no HTML, you are getting a 500 - Internal server error page. Theck your server logs.
I found this on my server error log. Your might be a different error:
[Sat Feb 16 10:57:10 2013] [error] [client 127.0.0.1] PHP Fatal error: Call to undefined function mysql_connect() in /var/www/question2answer/qa-include/qa-db.php on line 66
A search on stackoverflow revealed this often happens when you first install a LAMP server and recommends you to reboot.
After a reboot, it worked :)