I have a Multi Site install that looks like this:
main.dev.domain.com
testsite.dev.domain.com
dcdc.dev.domain.com
on main.dev.domain.com I can login as admin and do all the regular stuff (like change themes) but then when I go to the dashboards of the other sites, all I get is a login box where NOTHING works. I know in Network Admin I need to add the user to that domain and I've done that and the sites under "users" I see that user is enabled. However, when I go to testsite.dev.domain.com/wp-admin (the way to get to the dashboard of the site) I get a login box where no username and password work (not the one that I made when I setup the new site or admin which I enabled).
Is this by design? I finally changed the theme but I had to do it in edit site/setting where there is a long list of options and I just pasted in the theme path in there somewhere.
wp-config.php
network settings you were given. My guess is that the config file is confused by the domain and your cookies aren't being set correctly.