On my Enable Media Replace screen I get the following error after a WPMU 2.9.1.1 upgrade. It appears this may be a conflict with the Dynamic Content Gallery plugin.
Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'dfcg_add_page' was given in /home/websaum/public_html/wp-includes/plugin.php on line 339
Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'dfcg_options_init' was given in /home/websaum/public_html/wp-includes/plugin.php on line 339