Blank page for wp-admin/blog.php

On a new wordpressmu install, some users are seeing a blank page when they log into their blogs. This does not effect the primary blog, or the admin's user ID.

When a separate user (even a site admin) tries to login, on SOME of the blogs, they are directed to a wp-admin/blog.php page that shows as a blank page. They are being logged in according to the cookies on the machine. Could this have something to do with it? I have wordpressmu 2.8.4a and bbpress 1.0.3 installed and integrated.

Also, as the site admin, if I go to admin>blogs and then try to access any blog's backend other than the primary one, I am logged out to this page (example):

http://subdomain.example.com/wp-login.php?redirect_to=http%3A%2F%2Fsubdomain.example.com%2Fwp-admin%2F

I was having a login loop problem, but I have fixed that by adding
define( 'ADMIN_COOKIE_PATH', '/' );
define( 'COOKIEHASH', 'a683ed59f5ca34ac40dfb8062ee8983a' );
define( 'COOKIE_DOMAIN', '' );
define( 'SITECOOKIEPATH', '/' );
define( 'COOKIEPATH', '/' );

to the beginning of my wp-config.php file. Thoughts?

Man, I appreciate everyone out there who takes the time to help me through this. Eventually, I'll understand the trouble-shooting process better and give back to others. Cross my heart!

-james