It looks like you are hosted on GoDaddy, faced with the same issue, changing the .htaccess file to a subordinate one, fix it.
RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*) index.php?/$1
See http://ellislab.com/forums/viewthread/77847/
source share