Duplicate posts by admin since 3.1 upgrade

Ever since the 3.1 upgrade, our admin account has been getting comment and trackback notifications via email for content on other accounts in the installation. An investigation revealed that 158 of our 884 sites now have duplicate posts where the post_author field has been set to 1–265 posts to be exact. It’s more of an inconvenience for the admins, but I know that some of our users are going to be asking what’s up.

While this looks like a bug, perhaps there’s something else going on. Anyone have any thoughts? I suppose I could run a plugin that cleans up duplicate posts … but I’m wondering if other folks are having this problem post-3.1 upgrade.