You might encounter an error in your /etc/apache2/error.log stating:
[Tue Feb 01 00:57:02 2011] [alert] [client 192.168.1.102] /home/cliper/lampen/.htaccess:
Invalid command 'Header', perhaps misspelled or defined by a module not included in the server configuration
This is because mod_rewrite is not loaded. In my case, I suspected that mod_headers was not enabled.
So in terminal I did
and restart apache2
For hosted sites, you might contact your system administrator or in your cpanel.
Apache ver: 2.2.9 (Debian)