Trying to add new user to multisite installation

I have an installation that I converted (following the Codex instructions) to a network, or multisite, installation in order to add some microsites. I’m using subdomains (newsite.mysite.org for example) for the subsequent sites.

I need to add new users to my original blog, but have two issues. Before conversion, I was able to add users with username form “firstinitial.lastname”; now WP says no characters except numbers and lowercase letters!

And, the “add new users” screen doesn’t allow me to assign an initial password, which I had been doing previously, NOR to assign a user role. All those fields are just gone. How do I assign a role?

Are these issues the result of the network install? or did I do something wrong? I really need to be able to use that form for username. Perhaps it’s a theme issue? I’m using the free theme lithium (in child form) for the original blog.