When I try to add a new user (not an existing user in the network) to a site in our multisite network, I get a white screen after clicking Add New User. The user is NOT added to the site, but the user does show up in my Unconfirmed area. I then try to activate the user from there and get a message that says, this user cannot be activated. The user is STILL not added to the site, but is now part of the network.
I can add the user now as an existing user to the site, but this is a really long way to simply add users to sites.