I had this problem when following the CodeIgniter tutorial here: http://codeigniter.com/user_guide/tutorial/static_pages.html
The problem was I tried to access the url:
localhost/CodeIgniter_2.1.1/application/controllers/pages.php
instead of addressing the url:
localhost/CodeIgniter_2.1.1/index.php/pages/view
I know it has been around 18 months since you asked that question but maybe it can help someone else :)
