Clean URLs aren't being displayed
First thing I would check is the .htaccess is indeed working...maybe your getting a cached version of:

http://v6.dev/admin/config/search/clean-urls 

What happens when you enter a URI which you know has never existed (and been cached) such as:

http://v6.dev/xxx-237347-3iu33

Does it 404? Does drupal handle it and say "page cannot be found"?

I had a similar issue a few days back...I had to manually disable "clean uri's" in the database...flush all cache tables...re-enable mod_rewrite...log in and enable clean URI's

Let me know how you turn out. :)