I found several previous posts on this topic, but I'm not sure mine is related. I suspect I'm dealing with a plugin conflict, but I would like to run things by you all first:

I'm using the edu-clean theme on wpmu 2.7.1 and I installed the latest buddypress and bbpress this weekend. I logged out of bbpress and went to log out of wpmu from the front page of edu-clean and I get:

The generated url

The resulting logout URL

Too many redirects occurred trying to open “http://mysite.com/wp-login.php?action=logout&_wpnonce=398e2e09b9”. This might occur if you open a page that is redirected to open another page which then is redirected to open the original page.

Same if Logout from front page and from admin area and Buddy Bar

Same if I log into Forum as different user

Same if I log into Forum as the same user

I know that last week the logout worked. I confirmed that the theme link for the logout is: <?php wp_loginout(); ?>

So, basically, I can't log out of wpmu with any method that I'm aware of.