I've just created a brand new WordPress install, which works fine as long as I leave multisite as 'false'. Once I change it to true, i get an error saying there is no site defined at this host. wp-admin is also unreachable.
The extra DB tables for a multisite install are also not created.
When i switch the multisite parameter back to false in wp_config, I get a normal single-site install again.
The database for this site is on another server than the web files, might this be an issue? It's not for the single site install.
It is also the Dutch language version (from http://nl.wordpress.org/), might that be an issue?
These are the relevant config parameters:
define('WP_DEBUG', true); $base='/'; define( 'MULTISITE', true);