Maybe you are missing out the Directory directive for the aliased directory?
This configuration works fine for me:
[...]
DocumentRoot /web
[...]
<Directory /web/>
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
</Directory>
Alias /web2/ "/var/www/"
<Directory "/var/www">
Options FollowSymLinks
AllowOverride None
</Directory>
[...]