setting up main blog multi-authors not working for me

Hi:

I want to make members authors on the primary blog, but I'm having two kinds of trouble.

here's the production site (only the main blog exists now):
http://72.18.130.197/~hoopinst/

here's a summary of the situation:

1. I log in at site admin
2. go to My Blogs/Dashboard
3. I could add people to:
(sidebar)SiteAdmin/Users (which I would guess would be for the primary blog?)
or (sidebar)Authors & Users (which I would guess would be for member blogs?)

4. I've tried adding dummy members to both, and made them authors.

5. But, when I try to log in as these dummy members, I get one of two problems.

either I'm not able to post on the Primary blog (at this point, the only blog).
For example: as a site administrator, I go to SiteAdmin/Users to the dummy account 'multi1'. then I log in (when I can) as multi1, but when I make a blog post, it doesn't show up anywhere.

or

6. I can't log in at all from the home page, using the dummy member.

I'm sure I have some wrong settings somewhere, but have no idea where to look.

thanks for your help.