No 404 on existing folders

This is a somewhat wild guess, but shouldn't the following work (if placed before your existing rules)?

Code:

RewriteRule ^application/* - [F]

Thanks for your reply though it doesn't seem to work.

The most interesting part is that I loaded a fresh copy and there happens exactly the same. It being a subdomain throws errors at me, while it being a subfolder seems to work flawless. The only thing I want to achieve is remove index.php from the url, and the htaccess given above doesn't seem to work with that properly.

PS. The output is always "‹ãRàâxŽl" and the log always gives "ERROR - *time* --> 404 Page Not Found --> application"