I just upgraded to Domain Mapping 3.0.8, and now non-SuperAdmins cannot log in to their sites. It's a subdomain Network.
Checklist: I removed the old mu-plugin, uploaded the new plugin to the plugins folder, moved/overwrote the old sunrise.php file in the wp-content folder, then [re]activated the plugin.
As SuperAdmin, I can still log into all the site's admin areas. Regular Admins, and any other lower role, cannot log into their sites.
Result: They are thrown back (redirected) into the wp-login page
This occurs even if all plugins are deactivated.