Trouble setting up multisite

I’ve been trying to set up a wordpress multisite on both Media Temple and Blue Host hosting. In both cases I get through modifying .htaccess & wp-config.php, and adding blogs.dir in wp-content ok, and actually have a multisite running…

But then when I try to create new sites, the Network Admin panel thinks they’re just fine… but when you try to go to them there’s an error…

Am I missing a step?

TY!