Seems like there's a problem with the postmeta for the tags blog. Everytime a post is saved, duplicates are made, and the very first permalink meta_key is the direct one (for example: http://wisecracker.paidtoblog.com/?p=3). This can cause the permalinks to be returned incorrectly if a post has no revisions to it, as the last duplicate is always the one returned.
http://wordpress.org/extend/plugins/wordpress-mu-sitewide-tags/