Multisite Privacy Single Password issue?

Good morning, WPMU Dev Staff

We are running WP 3.4.1 (i.e. 1 domain, 3 sites by subdirectories) with the Multisite Privacy plugin (v. Our intent is to use a single password to restrict access to one of the three sites, while leaving the other two publicly available.

Everything looks right, but when we try to use the single password to access the protected site, it redirects us right back to the password prompt screen. No error message, nor "invalid password"-- just right back to the screen as if no password had been entered.

I'm guessing it might be related to the .htaccess file (maybe the redirect is getting thwarted by one of the rewrite rules?), but would appreciate any insight you can offer to help us resolve this issue.