I'm trying to get the Prologue theme working with WPMU (also running WPMU Sitewide Tags) and keep getting this error when posting an entry from the Prologue-themed blog:
PHP Fatal error: Call to undefined function wp_insert_category() in /path/to/wpmu/wp-content/mu-plugins/sitewide-tags.php on line 120, referer: http://myprologueblog.com/
That error corresponds with this line in sitewide-tags.php
wp_insert_category( array('cat_name' => $d, 'category_parent' => '') );
That line appears to run as expected (or at least without throwing errors) on other blogs. If I disable sitewide-tags.php the posts are published without error.