Ubuntu – 403 Forbidden problem with Apache

Strange, I have change folder users/groups to www-data (sudo chown -R www-data:www-data /datos/www) and also have changed permission to 755 (sudo chmod -R 755 /datos/www), but still getting 403 Forbidden problem with Apache. Tried to find out apache user in the process list and here is the result:

bakhtiyor@sony-vaio:/var/www$ ps aux | grep apache2
root      6627  0.1  0.2 158128  9244 ?        Ss   23:23   0:00 /usr/sbin/apache2 -k start
www-data  6632  0.0  0.1 158152  5348 ?        S    23:23   0:00 /usr/sbin/apache2 -k start
www-data  6633  0.0  0.1 158152  5348 ?        S    23:23   0:00 /usr/sbin/apache2 -k start
www-data  6634  0.0  0.1 158152  5348 ?        S    23:23   0:00 /usr/sbin/apache2 -k start
www-data  6635  0.0  0.1 158152  5348 ?        S    23:23   0:00 /usr/sbin/apache2 -k start
www-data  6636  0.0  0.1 158152  5348 ?        S    23:23   0:00 /usr/sbin/apache2 -k start
1000      6681  0.0  0.0  13468   896 pts/0    S+   23:23   0:00 grep --color=auto apache2

Apache configuration file for my virtual host is here:

<VirtualHost indextj:80>
    ServerAdmin webmaster@indextj

    DocumentRoot /datos/www
    <Directory />
            Options FollowSymLinks
            AllowOverride None
    </Directory>
    <Directory /datos/www/>
            Options Indexes FollowSymLinks MultiViews
            AllowOverride None
            Order allow,deny
            allow from all
    </Directory>
    ...
    ...
</VirtualHost>

Is it something related to the first process of apache that has been run under root? Even though I don't know why apache is running under root user.

Need some ideas about solving this strange issue.

Thank you