Multiple Plugin Conflicts with wpmu-users.php

Since I upgraded to MU 2.9.1.1 (and BuddyPress 1.2.1) I have issues with the users displaying properly under Site Admin > Users.

When all plugins are disabled the page loads fine. But most plugins cause the user page not to load completely. I’ve tried activating them one by one, some only cause a conflict in combination with another plugin. It’s hard to describe, but it seems to be a more general issue, and not necessarily related to individual plugins.

When a user is not completely displayed on the wpmu-users.php page (either completely missing, or only avatar missing, or blog associations missing) the user cannot access the blog dashboards of the blogs they are associated with.

I’ve tried everything short of installing a complete fresh copy of WPMU. Any ideas what could be causing this conflict? Thanks.