.htaccess redirect works for IP, but not for domain name

I have the following .htaccess file:

RewriteEngine   on
RewriteBase     /

RewriteRule     ^(/?)dir/?$            $1dir/subdir           [L]
RewriteRule     ^(/?)subdir2/?$        $1dir/subdir/subdir2   [L]

The redirecting works fine, if I type in the IP of the domain, but typing in the domainname/dir doesn't redirect me at all, instead shows me the content of the directory.

Another question: As I said, the redirecting with the IP works fine. However, although the 'R' flag is not set, the url changes in the url box. IP/dir changes into IP/dir/subdir. Why?

EDIT (11:20 GMT+1): Not quite sure if it's of any relevance, but before today the server didn't have a domain. I just bought a domain and set up all the nameserver pointing to the server up. Since I can access the page and it shows me the content of the /dir folder, I assume that I didn't mess up anything there.

EDIT (12:51 GMT+1): Output from apachectl -S:

apache2: Could not reliably determine the server's fully qualified domain name, using 0.0.10.188 for ServerName
VirtualHost configuration:
wildcard NameVirtualHosts and _default_ servers:
*:80                   is a NameVirtualHost
     default server 0.0.10.188 (/etc/apache2/sites-enabled/000-default:1)
     port 80 namevhost 0.0.10.188 (/etc/apache2/sites-enabled/000-default:1)
Syntax OK

EDIT (19:26 GMT+1): Found the problem. The problem was that my server name was not set and I had duplicates in ports.conf and httpd.conf, both where "listening". Thanks for pointing out the "apachectl -S" command. One mysterious problem left: Why is the url changing, although no R flag is set. Forever a mystery...